Scientific Program

Day 1

KEYNOTE SPEAKERS
  • Processing of T- MnAl

    Dartmouth college
    USA
    Biography

    Ian Baker obtained his BA and D. Phil in Metallurgy and Science of Materials from the University of Oxford. He is the Sherman Fairchild Professor of Engineering and Senior Associate Dean at the Thayer School of Engineering, Dartmouth College. He has published 400 papers and given over 300 presentations at universities, conferences and in industry, of which 150 were invited. He is a fellow of ASM, TMS, IOM3, MRS and AAAS. He is the editor in Chief of Materials Characterization.

    Abstract

    T- MnAl has an estimated maximum energy product, (BH)max, of 12 MGOe, which is twice that of AlNiCo magnets and is composed of much cheaper elements. On a density-compensated basis (BH)max for T- MnAl is almost two-thirds the value for SmCo magnets. In this presentation, we will outline various processing routes that we have used to produce powders of MnAl including gas atomization, rapid solidification processing using the Pratt and Whitney RSR process, and casting followed by pulverization. The resulting particulates were mechanically milled to produce nanocrystalline material using a Union Process attritor. The high temperature ?-phase was present both before and after milling along with significant amounts of equilibrium Y2 and ? phases. In addition, ribbons were produced by melt spinning, which had a similar mix of ?, ?and Y2 phases. We will outline the effects of annealing on the phases present and the magnetic properties of the various powders and ribbons. We will also present the results of the use of back-pressure assisted equal channel angular extrusion through which the powders are simultaneously consolidated and transformed to the T phase.

  • Metal hydride magnetocaloric compounds

    Institute of Chemistry and Materials Paris East
    France
    Biography

    Valérie Paul-Boncour has developed her expertise in the structural and physical properties of metal-hydrides systems since 1983. Hydrogen absorption in metal and intermetallic induces large structural changes (Cell volume increase, distortion, superstructure, amorphization) and significant modifications of the electronic and magnetic properties. She has developed an expertise in the hydrides of RMn compounds (R= Rare Earth, M=Mn, Fe, Co, Ni) which display a large variety of original structural and magnetic properties. She has also used the ability of tuning the magnetic properties by hydrogen absorption to synthetize magnetocaloric materials for magnetic refrigeration or heat pumps. She belongs to the Institute of Chemistry and Materials Paris East (ICMPE) created in 2007, which develops multidisciplinary research activities around four main areas: materials for energy, nano-materials and scale effects, materials for the environment and sustainable development, and chemistry at the interface with health and living.

    Abstract

    Classical refrigeration technology is using refrigerants (CFC, HCFC, and HFC) which deplete the ozone layer and contribute to global warming, and are or will be forbidden by different climate protocols. The alternative refrigerants (HFO, NH3, H2O …) present also various drawbacks. Therefore, it is important to develop new refrigeration technologies without environmental problems such as magnetic refrigeration based on the magnetocaloric effect (MCE). Development of efficient magnetocaloric materials (MCM) for magnetic refrigeration near room temperature has become challenging since the discovery of a giant MCE in Gd(Ge,Si)5 compounds. Intensive studies have yielded the development of several families of materials, among which the La(Fe,Si)13 type compounds which display a giant MCE, are not too expensive and are environmental friendly. We have developed a rapid method of synthesis and shaping magnetocaloric La(Fe,Si)13 compounds by combining high energy ball milling (BM) with reactive Spark Plasma Sintering (SPS) (Figure 1), a method which is already used to sinter and shape materials at an industrial scale. However, the Curie temperatures of these intermetallics, which is near 200 K, has to be increased near room temperature by Co for Fe substitution or light element insertion like hydrogen. The influence of combining both Fe for Co substitution and hydrogenation to increase TC above RT and extend the application of these materials to domestic heat pump and low-grade heat recuperation will be presented. We are also searching new MCM families. The Y1-xRxFe2(H,D)4.2 compounds (R=Gd, Tb) show a ferro(ferri)-antiferromagnetic transition which display a giant isotope effect and MCE. This transition is highly sensitive to any volume changes due to its itinerant electron metamagnetic behavior. The magnetocaloric properties of these compounds will be presented and we will show how the transition temperature can be shifted near room temperature by appropriate chemical substitutions.

  • Control ferromagnets at room temperature without external magnetic field

    Institute of Semiconductors
    China
    Biography

    Kaiyou Wang, PhD, Professor in Institute of Semiconductors in Chinese Academy of Sciences, Deputy Director of State Key Laboratory for Superlattices & Microstructure, obtained his PhD in 2005 at School of Physics & Astronomy, University of Nottingham. He worked as a Researcher Assistant from March to the end of May/2005 in University of Nottingham. He then worked as a Researcher in Hitachi Cambridge Laboratory from June/2005 to the end of March/2009. During his stay in UK, he had twice short visits to Institute of Physics, Poland and also a short visit to Niels Bohr Institute, Copenhagen. He joined State Key Laboratory for Superlattices & Microstructure, Institute of Semiconductors in CAS as a member of “100 Talent Program”. In 2012, he has been awarded the “National Outstanding Youth Foundation” from NSFC. In 2014, he was selected to be excellent in the “100 Talent Program” final assessment. His current research interests include: (1) spintronic devices; (2) physical properties based on low dimensional nano-electronic devices.

    Abstract

    Electrically controlling the spin in solids is the core of spintronics. We investigated that Spin Hall effect controls the magnetization switching in heavy metal/ferromagnet/heavy metal multilayers and also piezo voltages control the magnetization switching of Heusler alloy CoFeAl. By designing the device structure, we demonstrate a strong damping-like torque from the Spin Hall effect and unmeasurable field-like torque from Rashba effect. The spin-orbit effective fields due to the Spin Hall effect were investigated quantitatively and were found to be consistent with the switching effective fields after accounting for the switching current reduction due to thermal fluctuations from the current pulse. The spin-orbit torque switching controllably in above structures have to have the assistant of the external magnetic field. Without breaking the symmetry of the structure of the thin film, we realize the deterministic magnetization switching in a hybrid ferromagnetic/ferroelectric structure with Pt/Co/Ni/Co/Pt layers on PMN-PT substrate. The effective magnetic field can be reversed by changing the direction of the applied electric field on the PMN-PT substrate, which fully replaces the controllability function of the external magnetic field. We also investigated the planar Hall effect devices based on the tunability of the planar Hall resistance in ferromagnetic Co2FeAl devices solely by piezo voltages. The room temperature magnetic NOT and NOR gates have been demonstrated based on the Co2FeAl planar Hall effect devices without external magnetic field.

  • Advanced spintronic materials based on ordered alloys

    Tohoku University
    Japan
    Biography

    Koki Takanashi received his BS, MS, and Ph.D. degrees in Physics from the University of Tokyo. After postdoctoral research at Tohoku University, he joined the faculty there and is now a Professor and the Director of the Institute for Materials Research at Tohoku University. In 1994-1995 he was an Alexander von Humboldt Research Fellow at the Forschunszentrum Jülich in Germany. He has published over 350 papers and has receive numerous awards, including the Outstanding Research Award (2004, Magnetic Society of Japan), Outstanding Paper Award (2009, Japan Society of Applied Physics), Masumoto Hakaru Award (2011, Japan Institute of Metals). Professor Takanashi was the leader of a national project in Japan: “Creation and Control of Spin Current” (2007-2011). His research interests include magnetism and magneto-transport in nanostructures, magnetic materials for spintronics, and spin current phenomena.

    Abstract

    Materials used for spintronic devices should satisfy the following requirements like high spin polarization, leading to high efficiency in spin injection and high magnetoresistance, high magnetic anisotropy, leading to perpendicular magnetization and thermal stability of magnetization at reduced dimension and proper damping constant, leading to the optimization of the influence of spin transfer torque. It would be best to find a universal material that satisfies all these requirements; however, it is not easy. Starting from a material that satisfies one of each, usually, the way to extend the function by some modification of the material or to combine those materials might be adopted. We are interested in ordered alloys for spintronics, because some of ordered alloys show excellent functionalities such as high spin polarization and high magnetic anisotropy, and they are promising for the application to spintronics. Our group has been working on half-metallic Heusler alloys with high spin polarization, and demonstrated high CPP-GMR, which will be promising for the application to read heads in HDD. Co2MnSi/Ag/Co2MnSi, Co2FexMn1-xSi/Ag/Co2FexMn1-xSi and Co2FexMn1-xSi/Ag-Mg/Co2FexMn1-xSi epitaxial-layered structures were prepared by sputtering, and fabricated into pillar-shape by EB lithography for CPP-GMR measurements. The maximum MR ratio and the areal resistance change (?RA) obtained up to now are 62 % and 25 m?•?m2, respectively. CPP-GMR devices with half-metallic Heusler alloys also show high performance as spin torque oscillators (STOs) because of their low magnetic damping. A very high Q value of 4000 has been obtained with a power output of 10 nW.

Magnetism and Magnetic Materials | Functional Magnetic Materials | Magnetization Dynamics | Hard and Soft Magnetic Materials
Chair
Co-Chair
Speaker
  • Ternary phase soft magnetic coating on grain oriented electrical steel
    Speaker
    Sreedhara Sarma
    Tata Steel Europe
    United Kingdom
    Biography

    Sreedhara Sarma has completed his master’s degree from Loughborough University in 2008 and PhD at the age of 30 from the School of Engineering & Informatics, University of Bradford. He is a Project leader & Principal Researcher in R&D at Tata Steel, a premier steel manufacturing company. He has published papers in reputed journals along with three international patents in the relevant area of research.

    Abstract

    Looking at the power loss from transformer cores it accounts for approximately 5% of energy efficiency. In the European Union, there is an estimated 100 billion kWh total energy loss from transformers, which correlates to 40 million tons of CO2. In addition to this, some part of the energy is lost as transformer humming noise, which is a direct effect of magnetostriction phenomenon in grain oriented electrical steel (GOES). The loss could be reduced by improving the secondary recrystallization methods, grain orientation control, increasing the electrical resistivity of the steel, reducing the thickness of laminations and manipulating the domain structure. Applying coatings to GOES can also reduce the power loss by providing electrical resistance, improving magnetic permeability or the surface roughness as well as applying beneficial tensile stress. In order to improve the power loss, the coating selected must have a higher magnetic permeability and resistivity than GOES in order to reduce the power loss in this way. Aligned to the ternary phase metal alloy coatings were developed and applied to GOES through electroless and electroplating methods. The ternary phase coating applied on GOES improved the magnetic properties by applying beneficial tensile stress, which aligns the domains in the direction of magnetization and reduces the magnetostriction. There was also an improvement in the surface roughness, which reduces the number of pinning sites on the surface of steel.

  • Influence of the pressure on the multiferroic properties of the RMn2O5 series
    Speaker
    P Foury-Leylekian
    Univ. Paris Sud Université Paris-Saclay
    France
    Biography

    P Foury-Leylekian has completed her PhD and Post-doctoral studies from the Université Paris Sud, France. She was a Teacher at the Univeristé Paris Sud since 1996. She is currently working as a Professor at the Laboratory of Solid State Physics (LPS). She has published more than 70 papers in reputed journals.

    Abstract

    The RMn2O5 series of multiferroics is extensively studied for its strong magnetoelectric coupling, which results from a quasi collinear spin order and which is understood in the exchange-striction model. Variations of the interatomic distances modified by the external pressure can strongly influence the multiferroic properties. An amazing enhancement of the electric polarization has been observed in this series under pressure. Understanding this effect is of great importance from a fundamental point of view but also for the realization of multiferroic devices. We report here X-ray and neutron powder diffraction experiments performed under pressure on two prominent compounds of the family naming, PrMn2O5 and GdMn2O5. Indeed, PrMn2O5 is not ferroelectric at ambient pressure while GdMn2O5 presents the highest electric polarization of the series. In these compounds, we have evidenced new structural and magnetic phase transitions under pressure. These results provide key information to explain the pressure enhancement of polarization in the family. Moreover, they enable us to predict that PrMn2O5 become ferroelectric thus multiferroic under pressure, resulting in the first pressure induced multiferroic material.

  • Growth and Characterisation of Antiferromagnetic/Ferromagnetic Heusler Alloy Films
    Speaker
    Atsufumi Hirohata
    University of York
    England
    Biography

    Dr Atsufumi Hirohata joined the Department of Electronics in September 2007. He has over 15 years of experience in spintronics, ranging from magnetic-domain imaging to spin-current interference. He is currently an editorial board member of Journal of Physics D and Spin. He is also a member of both Administrative and Techical Committees of the IEEE Magnetics Society. He holds a visiting associate professorship at Tohoku University and a Royal Society Industry Fellowship in collaboration with Hitachi Cambridge Laboratory. Before coming to York, he was a researcher at RIKEN, a Japanese governmental research institute, for over two years, where he designed a spin-current interference device, which can be used as a spin operation in a spintronic three-terminal transistor. He was before working as a postdoctoral researcher at Tohoku University, and successfully fabricated a perfectly ordered epitaxial full-Heusler alloy films, which was the first report to their knowledge and was acknowledged by several awards. He also worked as a postdoctoral associate at Massachusetts Institute of Technology, where he demonstrated basic function of a phase-change memory, which has been recently released in a market by Intel. He received his PhD in Physics at the University of Cambridge in 2001 and then served as a research associate at the Cavendish Laboratory in order to complete his study on spin detection of optically pumped spin-polarised electrons in a semiconductor with using a ferromagnetic overlayers, which attracted great interest, resulting a few invited talks and papers. He was originally graduated from Keio University for his BSc and MSc studies in Physics.

    Abstract

    Further improvement of spintronic devices depend on the development of a new half-metallic ferromagnetic film. Heusler alloys are one of the most promising candidates to exhibit the half-metallicity (100% spin polarization) at room temperature with a large bandgap at the Fermi level. Even though such properties have been demonstrated in the bulk Heusler alloys, they are yet to be demonstrated in a film form unambiguously. According to the IEEE Magnetics Society Roadmap on Spintronic Materials , over 100% giant magnetoresistance (GMR) should be demonstrated based on the half-metallicity of the Heusler alloy films. Especially, those with perpendicular magnetic anisotropy is very important to be achieved. We have recently reported the perpendicular anisotropy using a body-centred cubic seed layer, such as vanadium and tungsten. For the Si//W/Co2FeSi structures, significant reduction in crystallisation energy is also achieved down to the annealing at 200ºC for 2 min. Such low temperature annealing with perpendicular magnetisation should be very useful for future device implementation. To characterise their interfacial properties of such devices, we have developed a new method using scanning electron microscopy. The beam is then decelerated using a negative bias on sample stage so that the beam penetrates only to the depth of an embedded junction (see Fig. 1). The generated backscattered electrons are selected by an energy filter attached near the detector to map conductance information from the junction. An energy dispersive X-ray spectroscopy is also used to identify the chemical compositions of the defects. Using this method, we have imaged Heusler alloy junctions to correlate their defects with their transport properties. This technique can be used for design and process optimisation of these junctions and can sustain an improvement in the density and functionality. This work was partially supported by the EPSRC (EP/M02458X/1), Royal Society Industry Fellowship, EC (NMP3-SL-2013-604398) and JST-PRESTO.

  • Phase diagram for the O(n) model with defects of “random local field” type and verity of the Imry-Ma theorem
    Speaker
    A S Sigov
    Moscow Technological University
    Russia
    Biography

    A S Sigov has his expertise in evaluation and passion in improving the theory of defect-induced anomalies of physical properties near phase transitions. Beginning his research and academic activity about 45 years ago, Alexander Sigov has published more than 200 papers on physical properties of real crystals near second-order phase transitions, ferroelectric and magnetic thin films&multilayers, microwave photonics, etc. He is the author of 30 extended reviews, monographs, and manuals for students. From the year of 1985 he holds the position of the Head of the Chair of Condensed Matter Physics at MIREA (later Moscow Technological) University. Sigov is professor emeritus, Fellow of the Russian Academy of Sciences (2011), has State and Government Awards for the achievements in physics, technology, and education (1999, 2008, 2010), is awarded the State Orders For Services to the Fatherland (2006) and Honour (2016).

    Abstract

    After the publication in 1975 the classical paper by Imry and Ma, the viewpoint was firmly established in the literature that at space dimensions d<4 the introduction of an arbitrarily small concentration of defects of the "random local field" type in a system with continuous symmetry of the n-component vector order parameter (O(n) model) leads to the long-range order collapse and to the occurrence of a disordered state, which in what follows will be designated as the Imry-Ma state and the statement given above will be named the Imry-Ma theorem. An anisotropic distribution of the directions of defect-induced random local fields in the order parameter n-dimensional space gives rise to the effective anisotropy in the system. Evaluation of the effective anisotropy constant Keff for strong anisotropic distributions in the order of magnitude gives the value Keff ~ x(hl)^2 /JS^2, where x is the defect concentration, hl is the local field induced by lth defect, J is the exchange interaction constant between neighboring spins and the brackets denote averaging over defects. The Imry-Ma theorem breaks down due to existence of the “easy axis” anisotropy induced by the defects designed initially for breaking down the long-range order. In the case of slightly anisotropic distribution of the fields, there exists a critical concentration of defects, if exceeded the Imry-Ma inhomogeneous state can exist as an equilibrium one. In the case of strongly anisotropic distribution of the fields, the Imry-Ma inhomogeneous state is completely suppressed and the state with the long-range ordering is realized at any defect concentration.

  • Identification of wall thinning of steel pipe using PEC spectrum Analysis
    Speaker
    Kyung-Ho Kim
    Korea Atomic Energy Research Institute
    North Korea
    Biography

    Kyung-Ho Kim has his expertise in the development the technology of materials properties measurement. He concentrated his passion in the nanotechnologies, which produce magnetic nano particle and its applications. He developed the technology to weld dissimilar metals using special filler materials. He also interested in the commercialization of technology, and served as a manager for this department in the Korea Atomic Energy Research Institute.

    Abstract

    The pulsed eddy current (PEC) system enables to detect the wall thinning and defects without removing the insulation, but the resolution is poor and data analysis is not easy. In this study we developed PEC system to detect wall thinning of Ferro magnetic steel pipes, which is capable of decimating the thickness change of pipe line through 95mm fiber glass thermal insulator and 0.4mmAluminum (Al) cladding. Peak amplitude and time to peak of the PEC signals obtained from various thickness regions of the test sample were analyzed in time domain. Results show a very good change corresponding to the sample thickness. In addition to time domain analysis, wavelet based signal processing technique was applied, in specific wavelet packet analysis based algorithm that utilizes the encoding technique was developed in MATLAB platform. Results were visualized and well accords with the time domain analysis.

  • Artificial magnetic lattices and their applications in optical and spin wave micro-devices
    Speaker
    Mitsuteru INOUE
    Toyohashi University of Technology
    Japan
    Biography

    Mitsuteru Inoue received Ph.D. from Toyohashi University of Technology (TUT) in 1989, and he is now Executive Trustee and Vice President of TUT. His expertise lies in the field of magnetic materials and their applications. In particular, he is interested in the interaction phenomena between spin system and various physical quantities including light (electromagnetic wave), acoustic wave, electron transport, heat transport. Recent his works are focused on materialization of novel functions with existing materials by introducing artificial structures. Along these works, he is now working on magnonics, in which spin waves are controlled by artificially introduced magnetic structures. He has published more than 250 full papers on the above fields. He was a visiting professor of Stanford University and Moscow State University. He received outstanding award from Magnetic Soc. Japan, and from Ministry of Education, Science & Technology, Japan.

    Abstract

    Introduction of artificial magnetic structures into existing magnetic materials sometimes produces novel functions to waves accompanying magnetism. Nano-scaled or submicron-scaled artificial magnetic lattices (AMLs), involving magnetophotonic, volumetric magnetic holograms4-5, even labyrinthian magnetic domain structures, for optical (electromagnetic) waves, and magnonic crystals for spin waves, can be classified into such materials. In this subject, fundamental properties of such AMLs mainly with magnetic garnet films and/or thin alloy films are discussed, followed by demonstrations of their applications in optical and spin wave micro-devices driven by magnetic phase interference: magneto-optic (MO) volumetric hologram memories and MO three-dimensional holographic displays6-8 both with magnetophotonic crystals; high-speed MO Q-switch micro-chip laser with iron-garnet films with labyrinthian magnetic domain structures9-10; and highly sensitive magnetic sensors and spin-wave logic circuits11-13 both with magnonic crystals. Prospective future technologies of spin wave devices with AMLs will also be discussed toward a new paradigm of magnonics (electron non-transport electronics), where spin waves play an important role as the information carrier.

  • Fabrication and application of Magnetorheological fluids
    Speaker
    Hyoung Jin Choi
    Inha University
    South Korea
    Biography

    Hyoung Jin Choi is Inha Fellow Professor at Inha University, Korea with BS from Seoul National University and Ph. D. in Chemical Engineering from Carnegie Mellon University in 1987. He joined Department of Polymer Science and Engineering at Inha University in 1988, and his research interests cover soft matter materials and complex fluids including electrorheology, magnetorheology, and polymer rheology. He is a member of Korean Academy of Science and Technology and a recipient of numerous scientific achievement awards including “World Class Research Front Award and Thomson Scientific Citation Laureate 2007 and the 2016 Top 300 Most Cited Researchers in Materials Science and Engineering by Elsevier Scopus Data.

    Abstract

    Magnetorheological (MR) fluids based on magnetically polarizable particles dispersed in non-magnetic fluids exhibiting a tuneable phase change from a liquid-like to a solid-like state by the application of an external magnetic field. In the absence of an external magnetic field, the magnetizable particles are dispersed randomly in the medium and the MR fluid exhibits Newtonian-like fluid behavior depending on the particle concentration. On the other hand, when a magnetic field is applied, the dispersed particles build up chain-like structures in the field direction due to an induced magnetic dipole–dipole interaction. Micron-sized carbonyl iron (CI) particles are the most widely applied commercial magnetic particles for MR fluids due to their high saturation magnetization and appropriate particle size; however, they are generally heavy to result in easy sedimentation in MR fluids. Hence, we have focused on improving the dispersion stability and MR performance of MR fluid with additive, such as hard magnetic ?-Fe2O3 nanoparticles, Halloysite clay, Fe3O4@SiO2, etc. In addition, synthesis of core-shell structured microspheres through the coating CI particles with PGMA, PANI, and SiO2@MWNT using a dispersion polymerization method, which improved the dispersion stability by reducing the density of magnetic particles. These kinds of particles based MR fluids were examined by a rotational rheometer under an extra magnetic field strength with steady shear and dynamic oscillation tests.

  • Exploring multiferroic materials for enhanced magnetoelectric coupling
    Speaker
    Anju Ahlawat
    Raja Ramanna Centre for Advanced Technology
    India
    Biography

    Anju Ahlawat (PhD - Physics), now is DST Faculty at Laser material Section, Raja Ramanna center for advanced technology, Indore (India). She got her B Sc and M Sc in Physics. She got her Doctor's degree (Ph.D.) in material science (Physics) from UGC -DAE Consortium for scientific research, Indore (India) in 2012 and a 4 years post doc experience from Raja Ramanna center for advanced technology, Indore, India. She has been working as Visiting Scientist at Martin Luther University, Halle, Germany for 6 months. She has got a prestigious research award from DST inspire Faculty in 2014. Currently Dr. Ahlawat’s research focus on novel multiferroic nanostructures for enhanced magnetoelectric coupling. She has published more than 20 papers in reputed journals.

    Abstract

    Magnetoelectric multiferroics represent a dynamic research topic motivated by both the need to understand the coupling mechanism and potential applications. Among the multiferroic family, the nanoscale heterostructured composites are of particular appealing due to their relatively high ME performance with respect to their single phase counterparts. The electric field manipulation of magnetic properties in multiferroics is highly demanding for the opportunities provided in low-energy-consuming spintronics devices. The present work focuses on the development of a ME nanocomposite films comprising of highly magnetostrictive magnetic (SmFeO3) and piezoelectric ferroelectric (PVDF) materials, which exhibits tuneable magnetoelectric response at room temperature. In this work, the manipulation of magnetic ordering with applied electric fields has been realized in polymer based magnetic thin films. Electric field poling induces significant change in magnetization and magneto electric response of composite films. Indeed SmFeO3 has excellent magnetic properties such as fast magnetic switching and an easy axis rotation transition (known as spin reorientation transition -SR) from c-axis to a-axis around 480 K. It is of particular interest for the magneto electric applications by utilizing its anomalous magnetoelastic properties near room temperature. The poling process produces sufficient strain in the ferroelectric PVDF matrix to reorient the magnetization of SmFeO3. Large magneto electric responses as well as good electric field control of the magnetization at room temperature makes these flexible composite films promising to be used for magnetoelectric sensors, memory storage and spintronic devices. Possible innovative applications have been addressed for these composites.

  • Heusler alloy thin films for data storage and energy
    Speaker
    Francesca Casoli
    Institute of materials for electronics and magnetism
    Italy
    Biography

    Francesca Casoli is a research scientist at the Institute of Materials for Electronics and Magnetism of the Italian National Research Council (IMEM – CNR). She obtained her PhD in Physics from the University of Parma in 2005, investigating magnetic thin films and multilayers with perpendicular anisotropy and exchange-spring properties. Her research is currently focused on Magnetic thin films, Nanostructures and Nanocomposites with new functionalities or multi-functionalities. She has published more than 60 peer-reviewed papers and 3 book chapters on magnetic materials for data storage, sensors/actuators and biomedicine. She has recently co-edited the book Ultra-High-Density Magnetic Recording: Storage Materials and Media Designs, edited by Pan Stanford Publishing in 2016.

    Abstract

    The more and more challenging requests of the data storage industry and new findings in the field of Spintronics have driven the interest of Magnetism research community towards the design and growth of thin films with high structural quality. Since the Nineties, several research groups have demonstrated the possibility to employ a sputtering apparatus to epitaxially grow, thin films of metallic alloys with different functional magnetic properties, e.g. huge magnetocrystalline anisotropy, ferromagnetic shape-memory, giant magnetoresistance. This demonstration has paved the way to the development of new devices, leading in some cases to important technological breakthroughs, as in the case of hard disk’s reading heads based on the tunnel magnetoresistance effect. We have used a RF sputtering apparatus to grow epitaxial thin films or heterostructures of different magnetic metallic materials, exploiting the alternate deposition from three targets to obtain specific and variable compositions of the alloys. Using single-crystalline substrates with different lattice parameters, i.e., MgO, SrTiO3, and LSAT, we have obtained epitaxial films (thickness from 10 to 200 nm) of two magnetic Heusler alloys: Ni-Mn-Ga and Mn-Ga. The films show a variety of different morphologies and microstructures, depending on substrate, film thickness and growth temperature. Our studies demonstrate that controlling structure and microstructure is crucial for tailoring magnetism. We have achieved a giant and anisotropic magnetization jump by microstructure engineering in magnetic shape-memory Ni–Mn–Ga films, which have a great potential for the fabrication of new-concept actuators, sensors and energy harvesters. We have also been able to epitaxially grow thin films of the metastable tetragonal phase of Mn-Ga (close to Mn3Ga composition); these films possess exceptional magnetic and electronic properties, which make them promising as ferromagnetic electrodes in Spin-Transfer-Torque Magnetic RAMs. For both these Heusler alloys, we have realized nanodots by self-

  • Research on Fe-based amorphous alloys with high-Fe content and excellent soft magnetic property
    Speaker
    Ke-Fu Yao
    Tsinghua University
    China
    Biography

    Ke-Fu Yao has his expertise in Developing Bulk Metallic Glasses and understanding their mechanical behavior and functional property. He developed a series of Pd-based bulk glassy alloys, Ti-based bulk glassy alloys, Fe-based glassy alloys and High-entropy glassy alloys with good glass-forming ability. He evidenced that some bulk metallic glasses could exhibit large compressive plasticity and good Magnetic property. He developed several methods for processing the amorphous alloys and improving their mechanical and functional properties.

    Abstract

    Iron based amorphous alloys (AAs) or metallic glasses (MGs) possess not only superior mechanical and anti-corrosion properties but also excellent soft magnetic property, which have attracted many attentions from both scientists and engineers. When used as magnetic materials, the Fe-based amorphous alloys are required to possess high saturation magnetization, which is closely related to the iron content. However, it is very difficult to prepare Fe-based AAs with high iron content due to their low glass-forming ability. As a result, only few Fe-based bulk amorphous alloys (BAAs) with Fe content close to 80 at% have been reported up to date. Then developing Fe-based BAAs with high Fe content and good soft magnetic property is meaningful. Recently, the effects of alloying elements and processing techniques on the glass-forming ability and the magnetic property of the high Fe content alloys have been studied in our group. It shows suitable alloying could significantly enhance the glass-forming ability of the high Fe content alloys. The Fe-based bulk amorphous alloys with the Fe content (or total magnetic elements content) of 80-82 at% have been successfully developed. In addition, these Fe-based bulk amorphous alloys exhibit good mechanical property and excellent soft magnetic property. Their saturated magnetic flux density (Bs) is about 1.60-1.65T. The present results indicate that it is possible to enhance the glass-forming ability and magnetic property of high Fe content alloys and develop high performance Fe-based BAAs.

Magnetism and Magnetic Materials | Magnetic Data Storage
Chair
Co-Chair
Speaker
  • Microwave heating mechanism of liquid crystals as revealed by microwave irradiation NMR spectroscopy
    Speaker
    Akira Naito
    Yokohama National University
    Japan
    Biography

    Akira Naito obtained his Ph D. from the Chemistry Department of Kyoto University, Japan, working with Prof. K. Akasaka on radiation damage of disulfide radicals as studied by ENDOR spectroscopy. He later worked as a post-doctral research fellow with Prof. C.A. McDoewell, University of British Columbia, Canada. Since 2001, he has been a Prof. in Yokohama National University, Japan. His main research interests are improving the magnetically oriented bilayer system and developing microwave irradiation and photo-irradiation solid-sate NMR spectrometers. He applied the microwave irradiation NMR to liquid crystal systems to reveal the microwave heating mechanisms and initiated state correlated 2D NMR spectroscopy [1,2]. He also applied photo-irradiation NMR to biological systems such as photoreceptor membrane proteins [3] to reveal the photoreaction processes.

    Abstract

    Microwave (MW) heating effects are widely used in the acceleration of organic and enzymatic reactions. These effects are primarily caused by the local heating induced by MW irradiation. However, the detailed molecular mechanisms associated with MW heating effects on the chemical reaction have not yet been well understood. This study investigated the MW heating effect of N-(4-methoxybenzyliden)-4-butylaniline (MBBA) in liquid crystalline and isotropic phases using in situ MW irradiation 1H NMR spectroscopy. The instrument used in this study consist of a solid state NMR spectrometer, equipped with a MW generator which is capable of transmitting 1.3 kW pulsed or continuous MW at a frequency of 2.45 GHz. A 3 mm wide flat copper ribbon was used to form the capacitor of the resonance circuit, and was wound coaxially inside the radio wave circuit. MWs were transmitted from the MW generator to the vicinity of the magnet through the MW, which served a coaxial cable and finally the MW were guided to the resonance circuit at the probe head. The application of MW irradiation at 130 W for 90 s while maintaining the spectrometer temperature at 20 ºC generated a small amount of isotropic phase within the bulk liquid crystal (Fig. 1 top). The partial transition to the isotropic phase can be attributed to a non-equilibrium local heating state induced by the MW irradiation. The application of MW at 195 W for 5 min to isotropic MBBA while maintaining a spectrometer temperature of 50 ºC raised the sample temperature to 160 ºC. However, CH3-O, and CH=N protons showed the temperatures at 220 and 350 ºC, respectively. It is revealed that the different protons indicated significantly different their temperatures within the molecule (Fig. 2 bottom). This result is realized as a distinctive microwave heating effect.

  • Anti-ferromagnetism in paramagnetic ion doped semiconductor nanocrystals
    Speaker
    Shun-Jen Cheng
    National Chiao Tung University
    Taiwan
    Biography

    Shun-Jen Cheng received Doctor rerum naturalium (Dr. rer. nat.), (Doctor of natural sciences) in physics from University of Würzburg, Germany in 2001, with the accomplishment of the thesis entitled “Collective excitations and Coulomb drag in two-dimensional systems” under the instruction of his supervisor Prof. Rolf. R. Gerhardts. In 2002, Dr. Cheng joined the “Quantum Theory group” led by Prof. Pawel Hawrylak at National Research Council of Canada in Ottawa, Canada, as Research Associate. In 2003, Dr. Cheng returned his home country and began his Professorship at Department of Electrophysics at National Chiao Tung University (NCTU), Hsinchu, Taiwan. He is currently Professor in physics at Department of Electrophysics at NCTU, Hsinchu, Taiwan. His research interests are in the theories of multi-exciton physics, magnetic-ion doped semiconductor nanostructures, and two- dimensional transition-metal dichalcogenides.

    Abstract

    Magnetism of a diluted magnetic semiconductor is known established mainly by those of individual paramagnetic ion dopants, which themselves are paramagnetic but interacting with each other anti- ferromagnetically. The anti-ferromagnetic (AFM) interactions are usually merged in the pronounced paramagnetism of magnetic ion doped nanocrystals and hardly exposed since the underlying AFM interactions are significant only between nearest neighbor magnetic ions, a portion of magnetic ion dopants, and do not essentially change the overall paramagnetic features. Nevertheless, the AFM interactions between magnetic ions in magnetic semiconductors have been extensively thought to significantly affect the magnetic features, including the reduced effective Mn concentration, fast spin relaxation, and low Curie temperature in the ferromagnetic phase. In this work, I will review our recent theoretical and experimental investigations of the magnetism of CdSe:Mn nanocrystals (NCs), where an efficient approach to the exposure and analysis of the hidden AFM in the paramagnetism of CdSe:Mn nanocrystals was proposed. Theoretically, the widely used exact diagonalization (ED) technique and mean field theory (MFT) are no longer applicable for the measured nanocrystals with the moderate number of Mn ions, typically 10~80 per NC. A key advance made in this work is the development of an analysis method that allows us to distinguish the anti-ferromagnetic interactions between aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic-ion-doped semiconductor nanocrystals. We build up a solvable model that still individually preserves each Mn spins and the exploitation of group theory technique to count the tremendously high degeneracies of the energy spectrum with no need of any heavy numerical computation. With the aid of the theory, we clearly reveal the signatures of AFM from the measured temperature dependent magnetic susceptibilities, and by fitting them with the theoretical calculations, we can estimate the number of Mn ions and even infer most probable spatial distributions of Mn ions.

  • Modeling non-linear magneto-elastic effects in hydrogels filled with ferromagnetic nanoparticles
    Speaker
    Olga Kuksenok
    Clemson University
    USA
    Biography

    Olga Kuksenok is currently an Associate Professor at the Materials Science and Engineering Department at Clemson University in Clemson, SC. She was formerly a Research Associate Professor at the Chemical Engineering Department at the University of Pittsburgh, Pittsburgh, PA. Dr. Kuksenok received her PhD in Physics and Mathematics from the Institute of Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine, in 1997. Dr. Kuksenok has co-authored over 80 peer-reviewed publications and 6 book chapters.

    Abstract

    Via theoretical and computational modelling, we focus on the gel composites filled with ferromagnetic nanoparticles uniformly dispersed within the gel matrix. For the polymer matrix, we choose Poly(N-isopropyl acrylamide) gels, which have lower critical solution temperatures (LCST) and hence undergo shrinking upon heating. When these composites are subjected to an AC EM irradiation with a frequency close to that of the Ferro-Magnetic Resonance (FMR) frequency, the absorbance of these samples increases dramatically. We show that this magnetic heating is sufficient to drive the volume phase transitions and results in a giant mechanical response of the sample (see Figure 1) for a feasible range of experimental parameters. We develop a model for the system that accounts for the dynamical coupling between the elastodynamics of polymer gel and interactions between the EM waves and ferromagnetic nanoparticles embedded within the matrix. This coupling is non-linear: as the system is heated and the gel layer undergoes shrinking at the temperatures close to the volume phase transition, the particles concentration increases, which in turn results in the increase in the heating rates (positive feedback). The gel elastodynamics is modeled based on the three-dimensional gel Lattice Spring Model, while the heating rate is calculated based on the approach developed in ref. 6. We elucidated conditions at which even a low power EM signal comparable to that used in various communication protocols can lead to a significant mechanical response of the gel, hence the gel’s motion can be effectively controlled by the remote low power EM signal. These results suggest a new design of active gel-based devices remotely controlled by the low power EM signals within the GHz frequency range.

  • Role of spin-charge coupling on antiferromagnetic universal scaling behaviors in unconventional Cu-based and Fe-based high temperature superconductors
    Speaker
    Sung-Ho S Salk
    Korea Academy of Science and Technology
    South Korea
    Biography

    Sung-Ho S. Salk has completed his Ph. D, in Physics, 1972 from the University of Texas at Austin. He was vice president of Korea Academy of Science (KAST) and Technology and is KAST permanent fellow. He has published more than 160 refereed papers in addition to book chapters, invited papers and talks and abstracts with the over 500.

    Abstract

    As well-known, the two different classes of Cu-based and Fe-based unconventional superconductors are characterized by antiferromagnetic and superconducting phases. One of the major theoretical challenges in high-Tc superconductivity is to understand physics involved universal scaling behaviors for both strongly correlated electron systems. In this study we focus our attention on the antiferromagnetic universal scaling behaviors of both systems based on our earlier proposed theory of the slave-boson founded t-J Hamiltonian of U(1) and SU(2) symmetry. This theory was successful in reproducing the observed phase diagrams of cuprate superconductors which show the monotonously decreasing pseudogap temperature and the dome-shaped superconducting transition temperature in the plane of temperature vs. hole concentration. The temperature and doping dependences of superfluid density and spectral function are well reproduced consistent with measurements. Besides, both charge dynamics and spin dynamics are importantly in good qualitative agreements with observed optical conductivity and spin susceptibility of involving magnetic resonance energy vs . All of these agreeable predictions are due to the spin-charge coupling which arises from our accurate derivation of the slave-boson founded t-J Hamiltonian which is not available elsewhere in literatures. This study further showed that the universal scaling behaviors in and are found in agreement with observations. Being encouraged we apply it to the Fe-based superconductors to show how well the universal scaling behaviors of the Cu-based superconductors fit ‘universally’ with them.

  • Linear acceleration over water surface by using magnetic strips
    Speaker
    Suresh Kumar Baliyan
    Saipem
    Saudi Arabia
    Biography

    Suresh Kumar Baliyan has completed his MTech from National Institute of Foundry and Forge Technology Ranchi, India. He is working as Planning Engineer from last 13 years in Oil and Gas Construction Company in Saudi Arabia. He has interest in experimenting with magnets/electrets. He has published one article and presented 1 paper at an international conference.

    Abstract

    Permanent magnets are known from thousands of years and this human eagerness to utilize magnetic force for useful work. Magnets have north and south poles, similar pole always repel and opposite poles attract each other. Accordingly, herein below I represent the model elucidating the study based on above theory. In my first experiment, I used the magnetic strips, which have thousands of poles on each edge. When a small magnetic strip is placed over water surface inside the disk, disk moves along the long magnetic strip as the water surface is efficient to detect a minute magnetic force in slow motion as shown in Fig. 1. The direction of force on small disk changes with change of orientation of small magnet inside disk over water surface. In second experiment, external magnetic strip is fixed with the outer circular bucket containing water and the internal magnetic strip is tied to the inner circular disk placed over the water surface as shown in Fig. 2. The continuous rotation of internal disk is by maintaining the fixed distance between two disks either point ‘A’ or ‘B’. If fixed distance is set at point ‘A’, the internal disk rotates clockwise and if the fixed distance is set at point ‘B’, the internal disk rotates anticlockwise. The clear visual process is shown in the video available in below link fixed distance is maintained by hand and can be easily possible to maintain by groove mechanism. A linear acceleration is generated along the magnetic strip in first case which is responsible for the motion of the small disk in both directions only by changing the inclination angle, and in second case the continuous force on the internal disk which makes the disk rotating over the water surface. Rotating motion is possible without hand (external) support by fixing the distance mechanically

  • Applications of rapidly solidified magnetic materials for structural health monitoring of engineering components
    Speaker
    Amitava Mitra
    CSIR-National Metallurgical Laboratory
    India
    Biography

    Amitava Mitra joined CSIR-National Metallurgical Laboratory, Jamshedpur, India, in the year 1990 after completing his PhD from India Institute of Technology, Kharagpur and Post-doctoral research from Applied Magnetism Lab., Spain. He has about 140 publications in reputed journals and 12 patents in the area of Magnetism and Magnetic Materials. He is recipient of US-AID and also JSPS invitation fellowship.

    Abstract

    One of the most popular ways of preparation of rapidly solidified soft magnetic materials is the melt-spinning of the molten alloys to form materials in the form of ribbon. The bulk use of these materials is the low loss transformer core materials. However, these materials have wide applications as sensing devices due to their superior properties due to the absence of magnetocrystalline anisotropy. One such application is the generation of ultrasonic guided wave using rapidly solidified Fe-Si-B based magnetostrictive ribbon for pipeline inspection. The system has been found suitable for detection of weld defect in pipeline. Even defects in underground pipeline were also demonstrated using magnetostrictive sensing device. In-water quenching of the melt is another way of preparing rapidly solidified materials in the form of wire. Nearly zero magnetostrictive materials in the form of wire exhibit Giant Magneto-Impedance (GMI) properties. The FeCoCrSiB based materials shows GMI ratio as high as ~500% in properly annealed state. Using such materials a sensing device has been developed named as MagSys which was used for damage assessment in petrochemical industries. During cracking of hydrocarbons in catalytic converter for refining of petroleum, carbon deposited which diffuses in steel during extended period of service. The diffused carbon in the steel component changes its composition and mechanical properties of steel deteriorate resulting in catastrophic failure. Such compositional changes can go to such an extent that a non-ferromagnetic stainless steel becomes very weakly magnetic. MagSys was used to find the extent of carburization in the Catalytic Converter Reactor Unit of a refinery unit of an oil company of India.

  • Study on the permanent magnetic properties of a series of W-type hexagonal ferrites
    Speaker
    Xiansong Liu
    Anhui University
    China
    Biography

    Xiansong Liu has completed his PhD from Nanjing University and Postdoctoral studies from Bar-ilan University. He is the Director of Engineering Technology Research Center of Magnetic Materials at Anhui and a Professor of Anhui University. He has published more than 80 papers in reputed journals.

    Abstract

    A series of substituted W-type hexagonal ferrites with composition Ba(Sr, La)Me22+Fe16O27 at different temperatures was synthesized by a ceramic process. The finely milled slurry with a diameter of 0.8 ?m was pressed into disk-shaped compacts in a pulsed magnetic field of 800 kA/m, which was parallel to the pressing direction. The phase composition, micromorphology, and magnetic properties of the particles were investigated by XRD, SEM and VSM. The permanent magnetic properties of the sintered magnets were measured by a B-H hysteresis equipment. The chemical composition of Sr1?xLaxZn2Fe16O27 (x=0-0.25) were synthesized. The results show that all the samples are a single phase as x below 0.20, which are the hexagonal structure and uniform distribution particles. The maximum values of the remanence (Br) and maximum energy product [(BH)max] for the magnets have been obtained at x=0.10. W-type hexagonal ferrites BaFe22+Fe16O27 have been successfully synthesized by the ceramic process in a nitrogen atmosphere during the process of pre-sintering and sintering. The permanent magnetic properties [Hcj, Hcb, Br and (BH)max] of Ba1-xSrxFe22+Fe163+O27 (0?x?1) magnets were obtained. The remanence (Br) of the magnets increases at first, reaches to the maximum value (402.4 mT) at x=0.3 shown in Figure 1 and then decreases. The maximum energy product [(BH)max] reaches the largest value (27.1 kJ/m3) in all the magnets.

Day 2

KEYNOTE SPEAKERS
  • Magnetic Impurities in cold atom systems

    Ben Gurion University
    Israel
    Biography

    Yshai Avishai did PhD at Weizmann institute. He is a professor of theoretical condensed matter Physics at Ben Gurion University, Beer Sheva Israel. He is a fellow of the American Physical Society, served as a Divisional Associate Editor for Physical Review Letters, was an Outstanding Referee for APS journals. He served as head of the Physics Department at Ben Gurion University, as head of the Ilse-Katz Center for Nanotechnology, as member of the Judging Committees for Israel prize in Physics and the Emet prize for exact Sciences. He is the author of 235 papers in high-level journals including Physical Review Letters and Nature, and an author of three books in Physics. He occasionally serves as Faculty Member at NYU-Shanghai University and YITP at Kyoto University, Japan. He visited and worked in numerous institutes around the world, Including Argonne National Laboratories, Lyon, Saclay, Orsay, Heidelberg, Tokyo, Kyoto, Hokkaido and others.

    Abstract

    Motivated by the impressive recent advance in manipulating cold fermionic atoms I will focus on two problems involving magnetic impurities. Experimentally it requires the preparation of a Fermi sea of cold atoms that are confined by a shallow harmonic potential and a trapping of a few other atoms (that serve as magnetic impurities) in specially designed optical potential. When there is an antiferromagnetic exchange interaction between the itinerant atoms in the Fermi sea and the localized magnetic impurity it gives rise to the Kondo effect. The first problem employs the fact that fermionic atoms can have spin s>1/2 and thereby the magnetic impurity is over-screened. At low temperature, such system displays a non-Fermi liquid behavior. We establish a theoretical analysis of interacting cold fermionic atomic systems that are governed by an effective Hamiltonian whose low energy physics displays an over-screening by large spin. In addition, we indicate candidate systems in which it can be experimentally realized. In the second part, we explore and substantiate the feasibility of realizing the Coqblin-Schrieffer model in a gas of cold fermionic Yb atoms. Making use of different AC polarizabillities of the electronic ground state) and the long lived metastable state, it is substantiated that the latter can be localized and serve as a magnetic impurity while the former remains itinerant. The exchange mechanism between the itinerant 1¬S0 and the localized 3P0 atoms is analyzed and shown to be antiferromagnetic. The ensuing SU(6) symmetric Coqblin-Schrieffer Hamiltonian is constructed. A number of thermodynamic measurable observables are calculated in the weak coupling regime $T>T_K$ (using perturbative RG analysis) and in the strong coupling regime $T

  • Effect of induced magnetic field on structure and properties of electrodeposited Ni-W alloy coatings

    National Institute of Technology Karnataka
    India
    Biography

    A. C. HEGDE is a M.Sc. graduate with Ph. D. from Mangalore University in 1993. He served successfully as Head of the Department of Chemistry for three years at NITK, Surathkal (2011-2014), and presently he is a Professor at the same department, and pursuing his research in allied fields of electrochemistry. He has published more than 100 research papers in peer reviewed Journals of National and International repute. He completed many R&D projects, and guided seven Ph.D., 17 B. Tech. and 20 M.Sc. students

    Abstract

    The effect of induced magnetic field on the process of electrodeposition of Ni-W alloy, and its water electrolysis character has been studied, with respect its intensity (0.1 T to 0.4 T) and direction (both parallel and perpendicular) of movement of metal ions. The experimental study revealed that electrodeposition under magnetic field, called magnetoelectrodeposition (MED) can be used as tool to alter the morphology, crystallinity and composition of the coatings, and thereby to increase its corrosion resistance and electrocatalytic activity for hydrogen evolution reaction (HER). The experimental results demonstrated that both corrosion resistance and HER activity of Ni-W alloy coatings has improved to many folds of its magnitude by MED approach. Drastic improvement in the performance MED coatings were attributed to the difference in process of electrocrystallization taking place under the influence of induced magnetic field, explained by magnetohydrodynamic (MHD) effect arises due to Lorentz force. The corrosion and electrocatalytic behaviors were tested using different electrochemical techniques. The experimental results were supported by advanced analytical techniques such as Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), and X-ray diffractometry (XRD), and experimental results were discussed with greater emphasis on the changed limiting current density (iL), affected due to applied magnetic field along with plausible mechanism.

  • Spin superfluidity, coherent spin precession and magnon BEC

    The Hebrew University of Jerusalem
    Israel
    Biography

    Edouard B Sonin is an Emeritus Professor at the Hebrew University of Jerusalem, Israel. His research interests focus on the superfluidity theory and the vortex dynamics in superfluids, superconductors, and magnetically ordered materials. He has over 230 publications including two books.

    Abstract

    Spin superfluidity, coherent spin precession, and magnon BEC are intensively investigated theoretically and experimentally nowadays. Meanwhile, clear definition and differentiation between these related phenomena is needed. Spin superfluidity is defined as a possibility of dissipation less spin transport on macroscopical distances with sufficiently large spin supercurrents. This possibility is realized at special topology of the magnetic-order-parameter space, such as, e.g., that in easy-plane ferro- and antiferromagnets, or in coherent precession states supported by pumping of energy and magnons. Recent claims on experimental observation of spin superfluidity (in yttrium-iron-garnet magnetic films, in particular) are discussed.

Electromagnetism | Nanomaterials and Nanotechnology | Materials Science and Engineering | Superconductivity and Superfluidity | Spintronic Effects and Devices
Chair
Co-Chair
Speaker
  • Application of Magnetic Field for Enhancement of yield in Soybean and Maize
    Speaker
    K N Guruprasad
    Shri Vaishnav Vidyapeeth Vishwavidyalaya
    India
    Biography

    Dr K N Guruprasad has completed his Ph.D. in 1979 from Gujarat University and Joined as a Lecturer 1981 in School of Life Sciences, Devi Ahilya University and then Reader in 1987 and Professor in 1994 till his retirement in March 2017. Under his guidance, 23 students completed Ph.D. He has published 85 papers in reputed journals and 02 book chapters.

    Abstract

    Soybean and Maize seeds were pre-treated with static magnetic field (SMF) of 200 mT for 1 h to evaluate the effect of magnetopriming on growth and yield characteristics under field conditions. Presowing SMF treatment of seeds with 200 mT (1 h) persisted in soybean and maize plants under field conditions till its maturity. SMF pre-sowing treatment showed significant enhancement in plant height, leaf area and biomass accumulation in both the crops. Nitrate reductase activity, photosynthetic pigments, leaf photosynthetic efficiency, leaf protein content and net rate of photosynthesis and stomatal conductance were significantly increased after SMF pre-sowing treatment as compared to the untreated controls. Thus pre-sowing exposure of seeds to SMF enhanced carbon and nitrogen metabolism and improved the yield in both soybean and maize. All the yield parameters of soybean like- number of pods, number of seeds per plant and seed weight per plant and yield parameters of maize like- weight of cobs/plant, number of seeds/cob and weight of seeds/cob were enhanced by SMF pretreatment of 200 mT (1 h). Magnetopriming of dry seeds of soybean and maize can be effectively used as a pre-sowing treatment for improving plant growth and yield under field conditions.

  • Magnetic transistor and sensor based on Varistor diodes
    Speaker
    R K Pandey
    Texas State University
    USA
    Biography

    R K Pandey is currently a Professor of Ingram School of Engineering at Texas State University, San Marcos, TX. There until two years ago he was the inaugural holder of the endowed Ingram Professorship. Before joining at TSU in 2008 he served at Texas A&M University, College Station, TX for 20 years (1977-97) and at the University of Alabama, Tuscaloosa, AL for another 10 years (1997-2007). He is a Professor Emeritus of both these universities. He is a researcher of international stature with recognized contributions in Electroceramics, high temperature superconductivity and magnetism. In the last five years, he has pioneered the fields of “Varistor-transistor hybrid devices” and “Varistor dependent magnetic sensors.” He is the lead inventor for 10 US patents. He has published extensively in national and international scientific journals, has travelled abroad for presenting invited lectures and seminars and has received multiple teaching and research awards.

    Abstract

    The varistor diode is typically used for circuit protection. However, its bipolar current-voltage (I-V) characteristics can be modified to produce hybrid devices having the attributes of a transistor and a magnetic sensor. The modifications are induced with the application of an electric or magnetic field. By tuning the I-V characteristics with an electric field we have produced a hybrid device that can be used either as a varistor or an electric field effect (E-FET) transistor. The paper will describe how this can be achieved using a varistor based on a ceramic IHC 45 (ilmenite-hematite ceramic) substrate. The E-FET attributes are comparable to those of a bipolar junction transistor. The high level of signal amplification and transconductance of the E-FET device exceeds the values normally found in commercially available bipolar transistors. Also the varistor itself acquires the properties of signal amplification and transconductance while still retaining its basic function of circuit protection. All these devices are particularly suitable for high temperature operations. Furthermore by tuning the voltage dependent resistance (VDR) mode of the varistor by a magnetic field one can produce magnetic sensors that can detect the magnetic field in the range of 150

  • Electron acceleration by Chirped axicon Gaussian laser in vacuum
    Speaker
    Niti Kant
    Lovely Professional University
    India
    Biography

    Niti Kant is Associate Professor at Physics Department at Lovely Professional University, Phagwara, Punjab, India. He received Ph.D. degree in Laser-Plasma Interaction from IIT Delhi. His research is focused on the areas of self-focusing of lasers in plasmas, laser-plasma based accelerators and THz radiation. He was Postdoc Fellow at POSTECH, South Korea from Dec. 2005 to Feb. 2007. He has supervised 04 Ph.D., 11 M.Sc. and10 M.Phil students and supervising 3 Ph.D. & 2 M.Sc. students. He has published more than 45 research papers in international refereed journals and participated various national/international conferences.

    Abstract

    Electron acceleration by Frequency chirped radially polarized (RP) axicon Gaussian laser pulse in vacuum in the presence of wiggler magnetic field is studied. A strong longitudinal electric field is produced by axicon Gaussian laser pulse which is crucial and responsible for direct electron acceleration in vacuum. Linear frequency chirp enhances the interaction time between laser and electron however, the applied wiggler magnetic field helps in improving the strength of ponderomotive force so that the electron traversing in the accelerating phase up to longer distances. It is observed that an electron with initial energy of few MeV accelerates up to GeV energy with optimized laser and magnetic field parameters. A significant enhancement in the electron energy gain is seen in the presence of wiggler magnetic field.

  • Features of tunnel magneto resistive effect in various types of nanocomposites
    Speaker
    Oleg V Stognei
    Voronezh State Technical University
    Russia
    Biography

    Oleg V Stognei has completed his PhD in 1990 in Voronezh Polytechnic Institute (Russia). He worked as an assistant professor and then as a professor at the Department of Solid State Physics in Voronezh State Technical University (Russia). The science interests are electrical and magnetic properties of nanostructured materials (nanocomposites and multilayers). As an invited researcher carried out investigations in Royal Institute of Technology (Sweden) and PTB (Germany). He has published more than 100 papers in reputed journals.

    Abstract

    An overview of the experimental data concerning the study of tunnel magneto resistive effect (TMR) in different type of nanocomposite (ferromagnetic-dielectric and ferromagnetic–semiconductor) prepared on the same equipment and under similar conditions has been made. The influence of material of ferromagnetic phase (CoFeB, CoNbTa and CoFeZr) on the magnetoresistance has been investigated in composites with amorphous metal granules. At the similar morphology of the composites and absent of a crystalline anisotropy in ferromagnetic granules the TMR values depends on the properties of metal phase. The maximum values of TMR and saturation magnetostriction of the metallic phase as well as maximum values of the Kerr effect are in composites, containing metal granules which have higher density of electron states at the Fermi level (g(?F)). In studied systems it gives following sequence: CoNbTa ® CoFeB ® CoFeZr (fig.1). In a case of crystalline granules, the positive magneto resistive effect is being added to usual negative TMR (see fig.2). The positive effect is observed in Co-Al2O3, Co-SiO2, and Co-MgF2 composites and is due to complicated morphology of the composites: simultaneous co-existence of clusters and separated nanogranules having different anisotropy. The positive magnetoresistance is not observed in every crystalline composite, for example it is not observed in Co-CaF2 system. According to HRTEM this system has another morphology. One can suppose that the ratio between surface energy of metal and dielectric phases is responsible for the composites morphology and for presence or absence of the positive effect. In a case of semiconductor matrix the composites also exhibit tunnel magnetoresistivity but the value of the effect is much smaller. Comparison of the TMR values of Fe-Nb2On and Ni-Nb2On composites with Fe-Al2On and Ni-Al2On gives the conclusion: magnetoresistance in composites with semiconductor matrix is one order smaller than in composites with dielectric matrix. But the current mechanisms in composites with different type matrix are the same: tunneling of electrons between granules and tunneling of electrons via localized states.

  • Magnetic energy optimization of Cobalt-based nanostructured magnet
    Speaker
    Silvana Mercone
    Paris-Sorbonne University
    France
    Biography

    Silvana Mercone is an Associate Professor of the LSPM-CNRS laboratory at University of Paris 13th. She obtained the “Italian Laurea” in Solid State Physics at University of Rome “La Sapienza” in 2000 and her PhD sponsored by Marie Curie fellowship (EC) in Material Science in 2003 at the University of Caen (Normandy, France) - Laboratory CRISMAT. She became Assistant professor in 2006 after 3 years of post-graduate fellowships. She has mainly worked on magnetic of complex nanostructures (thin films and devices, nanoparticles and nanowires) focusing on the coupling between the crystallographic properties and their magnetic and transport behavior (magnetic phase separation (AFM-FM), metal-to-insulator transition, magnetoresistance). She has a good experience and knowhow on a broad number of experimental technics allowing the full study of the static and dynamic magnetic behaviour of complex magnetic materials (SANS and Polarized Neutron Reflectivity for magnetic phase homogeneity investigation, Broadband ferromagnetic resonance and electron paramagnetic resonance, SQUID, VSM).

    Abstract

    Co-based anisotropic nanowires are attracting scientific interest mainly for their possible applications as nano-magnets in (nano)medicine as well as in recording media and as building blocks in high energy nanostructured bulk permanent magnets. In this latter case, a high magnetocrystalline anisotropy of the ferromagnetic nano-object is essential for high magnetic coercivity which are mandatory for obtaining a high magnetic energy product (namely BHmax) and thus a good permanent magnet. In this frame, we studied the magnetic static properties of hcp-cobalt nanowires, which show a high shape anisotropy and magnetocrystalline anisotropy by using a standard Quantum Design MPMS SQUID magnetometer in the temperature range of 5 - 400K and with a magnetic field applied between -7 Tesla and +7 Tesla. The magnetic energy of these nanowires has been studied as a function of the shape as well as of the stacking fault, respectively determined by HRTEM and X-Ray diffraction measurements. The optimum candidates have been sintered by non-conventional SPS technique and cobalt-based nanostructured materials have been studied in view of magnetic energy optimization. A micromagnetic simulation was performed to study the local interactions of nanowires inside the like-bulk nanostructured samples. Our results show that the magnetic energy product of the Co nanowire is strongly affected by the shape ratio (L/d) as well as by the stacking fault density (?). When the aspect ratio is optimized (L/d>10), the stacking fault density is the key parameter to control the BHmax (voir Fig.1). A huge loss in the magnetic energy is discussed as function of the changing interactions between nanowires. We also present the sintering process parameter effects over the BHmax product at room temperature, and we discuss future issues and solutions for new nanostructured magnet elaboration.

  • `Structure-Property Correlations of Magnetic Nanoheterostructures
    Speaker
    Sayan Bhattacharyya
    Indian Institute of Science Education and Research
    India
    Biography

    Sayan Bhattacharyya obtained his Ph.D. with Prof. N. S. Gajbhiye at the Indian Institute of Technology, Kanpur, India in 2006. He completed Postdoctoral research with Prof. (Emeritus) Aharon Gedanken at Bar-Ilan University, Israel (2006-2008) and Postdoctoral research with Prof. Yury Gogotsi at Drexel University, USA (2008-2010). He Joined IISER Kolkata in April 2010 and became Associate Professor of the Department of Chemical Sciences, IISER Kolkata since February 2015. At present, he is the Founder & Head of the Centre for Advanced Functional Materials. He is a Materials Chemist interested in magnetism, photovoltaics, catalysis for energy and drug delivery. A combination of wet-chemical synthesis and self-assembly of smart nanomaterials, structure-property correlation and device applications are used to attain these research goals. In 2017, Dr. Bhattacharyya has been highlighted as, one of the Emerging Investigators by the prestigious Journal of Materials Chemistry A, Royal Society of Chemistry. He is member of the American Chemical Society (ACS), invited member of the American Nano Society, lifetime member of the Chemical Research Society of India (CRSI), member of the Association for Iron & Steel Technology (AIST), 2009, PA, USA, and member of the American Ceramic Society, 2009, USA.

    Abstract

    Magnetic ceramics are important materials for a variety of applications such data storage, tunnel junctions, spin valves, sensors etc. These materials possess extra-ordinary properties at reduced dimensions. The properties of nanostructures are governed by finite size of the particles, lattice distortions and grain boundary effects. In the first part of this lecture the structure-property correlations of Pr1-xCaxMnO3 (PCMO, 0.0 < x ? 0.5) nanoparticles (NPs) will be discussed. Although PCMO at x < 0.1 is conventionally antiferromagnetic (AF), ~40 nm diameter PCMO NPs demonstrate ordering of Pr spins below 50 K with x < 0.04. Even in absence of Ca2+-doping, ~35 nm PrMn0.9O3.01 NPs show ferromagnetism below 100 K due to the increase in bond angles. Riveted analyses of the X-ray diffraction patterns from 300 to 10 K could successfully mirror the four magnetic phases viz. paramagnetic, AF, ferromagnetic (FM) and spin glass ordering. In second part of the lecture, the effect of electron polarization across the grain boundaries of 20 nm La0.72Sr0.29MnO3 (LSMO) NPs in demonstrating an unusually large 29.8% low-field magnetoresistance (LF-MR) at 30 K with 50 mT-applied fields will be discussed. The MR in LSMO NPs is influenced by the surface and re-entrant spin glass states below 30 K. In the third part, exchange bias (EB) effect at AF/FM interfaces in the nanostructures to increase the coercivity and anisotropy of the systems will be considered. Although EB is observed under applied cooling fields, spontaneous EB (SEB) is observed at 5 K under zero-field cooling in the stacked 10-14 nm thick PCMO nanosheets, synthesized by pressure-assisted transformation of metal acetates. High ferromagnetic moments and SEB are attributed to the long-range magnetic interactions in the stacked 2-dimensional arrangement of Mn3+/Mn4+ d-electron spins. Apart from manganite nanosheets, inverted EB nanostructures are equally interesting. One such system was designed where 3.4 wt% of ~9 nm NiO NPs are inserted inside the pores of 30-40 nm clustered CoFe2O4 particles. The role of in situ embedded NiO NPs is to introduce AF/ferrimagnetic exchange coupling to provide a hysteresis loop shift of 233 Oe at 5 K with a cooling field of 2 T.

  • Perpendicular magnetic anisotropy and its reorientation in two-dimensional structures
    Speaker
    Dorj Odkhuu
    Incheon National University
    South Korea
    Biography

    Dorj Odkhuu has completed his PhD in Physics from University of Ulsan 2014 and postdoctoral studies from Ulsan National Institute of Science and Technology and California State University Northridge. He is currently an assistant Professor at Incheon National University, South Korea. His research focuses on first-principles calculations of magnetic and magnetoelectric materials and he has published more than 40 papers in peer-reviewed journals.

    Abstract

    Exploring magnetism in otherwise nonmagnetic two-dimensional materials, such as graphene and transition metal dichalcogenides, is at the heart of spintronics research. In this talk, we will present our recent findings on the possibility of reaching an atomic-scale perpendicular magnetic anisotropy by carefully exploring the large spin-orbit coupling, orbital magnetism, and ligand field in a suitable choice of a two-dimensional material with transition metal ad atoms. We will also discuss towards promising approaches for manipulating magnetism and magnetization vector in two-dimensional nanostructures by an external stimulus, that is, forming the tetrahedral sp3-metallic d hybrid bonds, strain effect, or applying an electric field.

  • Magnetomigration of rare-earth ions in strong magnetic fields
    Speaker
    Isadora R Rodrigues
    KU Leuven
    Belgium
    Biography

    Isadora R Rodrigues obtained a Master’s degree in Chemistry in 2010, at the University of Montreal, Canada. The topic of her thesis was the synthesis and characterization of cathode materials for Li-ion batteries. In 2016, she joined the Department of Material Engineering at KU Leuven University (Belgium), to start her PhD on the topic of Magnetic Separation of Rare-Earth Ions. She is author (or co-author) of 6 publications in international journals.

    Abstract

    The use of magnetic fields to manipulate macroscale particles is a well-known method applied to the separation of magnetic materials. The energy of paramagnetic species exposed to an external magnetic field decreases as the magnetic force pulls them towards stronger magnetic fields. The opposite occurs for diamagnetic species, which tends to move to regions with weaker fields. Encouraging results are found in the recent literature for the magnetic separation of paramagnetic ions. However, the effect of external magnetic fields on small molecules and ions is rather controversial. The magnetically induced movement of single ions in solution is likely to be overpowered by the high kinetic energy of the system due to Brownian collisions. In the present work, Mach-Zehnder interferometry (MZI) was used to study the magnetomigration of rare-earth (RE) ions. Two RE ions were selected for the experiments based on their distinct magnetic properties: the strong paramagnetic Dy3+ (magnetic susceptibilities ?>0) and the diamagnetic Y3+ (magnetic susceptibilities ?<0). No migration of ions was found for a thermodynamically closed system when a perfectly homogeneous solution was subjected to an external magnetic field. However, when a concentration gradient was introduced in the sample by solvent evaporation, consistent migration of paramagnetic Dy3+ ions was observed, from the bulk solution to regions with stronger magnetic fields (Figure 1a-b). By contrast, no movement was detected for diamagnetic Y3+ ions, notwithstanding the presence of a concentration gradient.

  • From high-spin single molecule magnets to low-spin single ion magnets
    Speaker
    Roman Boca
    University of SS Cyril and Methodius in Trnava
    Slovakia
    Biography

    Roman Boca has completed his PhD at the age of 27 years from Slovak University of Technology in Bratislava, Slovakia. He is professor of chemistry since 1993, presently at the University of SS Cyril and Methodius in Trnava, Slovakia. He has over 300 publications that have been cited over 3000 times, and his publication H-index is 33. His main scientific focus was quantum chemistry of coordination compounds and presently the theoretical and experimental molecular magnetism [A Handbook of Magnetochemical Formulae, Elsevier, Amsterdam 2012; Theoretical Foundations of Molecular Magnetism, Elsevier, Amsterdam, 1999].

    Abstract

    Nanomagnets such as single molecule magnets, single chain magnets, and single ion magnets attract an explosive interest in the recent years. Earlier studies on polynuclear complexes, such as Mn12 and Fe8 prototypes, were motivated by the high-spin ground state (S = 10); however these rather symmetric systems displayed only a slight magnetic anisotropy (D < 0). Investigation of the lanthanide (Dy and Tb) complexes brought much higher magnetic anisotropy and consequently much higher barrier to spin reversal that conditioned a prolongation of the relaxation time. A return to the 3d transition metal complexes caused a breakdown in investigation of single ion magnets with plethora examples of them in the family of tri-, tetra-, penta-, hexa-, hepta- and octacoordinated Co(II) complexes with the spin S = 3/2. Only three mononuclear Ni(II) complexes with S = 1 display the slow magnetic relaxation in the AC magnetic fields [Dalton Trans. 2015, 44, 12484]. There are a few reports on S = 1/2 spin systems spanning the class of single ion magnets: mononuclear complexes of V(IV), Mn(IV), Ni(I) and Cu(II) belong to them [Inorg. Chem. 2017, 56, 1478]. Unlike the traditional single molecule magnets, the slow magnetic relaxation in low-spin single ion magnets is dominated by the Raman, direct, and the quantum tunneling processes.

  • Electric field and strain control of magnetism: Towards ultralow energy memory devices
    Speaker
    Nicholas G Kioussis
    California State University Northridge
    USA
    Biography

    Nicholas G Kioussis has completed his PhD from University of Illinois at Chicago and postdoctoral studies from West Virginia University. He is the founder and director of the W. M. Keck Computational Materials Theory Center at California State University Northridge. He has published more than 150 papers in reputed journals in the areas of Electronic structure calculations, Multiscale modeling of defects, strongly correlated electron systems, spin transport in magnetic tunnel junctions, and topological insulators and Weyl semimetals. He served as the Director of several International Workshops on Correlations Effects and Materials Properties. Awards include DOE Faculty Fellowship, Lawrence Livermore National Laboratory, Marie Curie Fellowship, Outstanding faculty award, US Air Force Fellowship, Wang Family Excellence Faculty Award.

    Abstract

    Voltage-controlled magnetic anisotropy (VCMA) plays a central role in the operation of the next-generation of ultralow energy, non-volatile, magneto-electric random access memory (MeRAM). The major challenge in the development of the next-generation MeRAM is the low (< 100 fJ/(Vm)) magnetoelectric (ME) coe?cient which in turn leads to high switching bit energy and high write voltage. Employing ab initio electronic structure calculations we demonstrate for the first time that epitaxial strain, which is ubiquitous in many heavy metal (HM)/ferromagnet (FM)/insultor trilayers, has a dramatic e?ect on VCMA of the HM/FeCo/MgO heterostructures (HM=Ta, Au, Hf). Strain can give rise to a wide range of novel VCMA behavior shown below where the magnetic anisotropy can change from ?- to a ?-shape E-field dependence with giant ME coe?cients which are asymmetric under voltage reversal. By tuning the epitaxial strain the ME coe?cient can reach values as large as ?1800 fJ/(V.m) which in turn lead to magnetic switching in the low-E-?eld regime. The underlying mechanism is the interplay between the modi?cation of the MgO dielectric constant by strain and the changes of the spin-orbit coupled d-states at the interfaces due to the synergetic e?ect of strain and electric ?eld. I will also present results of manipulation of the magnetization direction of ultrathin FeRh/insulator bilayers in the antiferromagtic or ferromagnetic phase by purely E-field means (rather than E-field induced strain). I will show an E-field magnetization switching with giant voltage controlled magnetic anisotropy efficiency and a spin reorientation across the metamagnetic transition. These findings open interesting prospects for exploiting strain engineering to harvest higher efficiency VCMA for the next generation MeRAM devices based on ferromagnetic and antiferromagnetic materials. This research was supported by NSF Grant No. ERC-TANMS-116050.

  • Antiferromagnet-based tunnel junctions
    Speaker
    Cheng Song
    Tsinghua University
    China
    Biography

    Cheng Song has completed his PhD at the age of 27 years from Tsinghua University and Postdoctoral studies from University of Regensburg. He was a Humboldt fellowship, and now is an associate professor in Tsinghua University, working on magnetic films and spintronic devices. He has published more than 120 papers in reputed journals with citation >3500 and has been serving as an editorial board member of Scientific Reports.

    Abstract

    Antiferromagnet (AFM) spintronics have emerged as a fascinating research area and stimulated intense interest due to their potential for ultrafast and ultrahigh-density spintronics. Magnetic tunnel junctions (MTJs) with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance (TAMR) dependent on the anisotropic density of states, but no room temperature performance so far. After the observation of TAMR at room temperature in antiferromagnet- based junctions, recently we provided an alternative approach to obtaining TAMR in ?’-FeRh-based MTJs driven by the magnetic phase transition of ?’-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance (PT-TAMR). The MTJs with only one ?’-FeRh magnetic electrode show a PT- TAMR ratio up to 20% at room temperature. Both the polarity and magnitude of the PT-TAMR can be modulated strongly by interfacial engineering at the ?’-FeRh/MgO interface. Besides the magnetic field, some recent progresses on the modulation or switching of antiferromagnetic stacks by electrical means, electric field and current would be also briefly discussed in this talk. These findings might add a different dimension to magnetic random access memory and antiferromagnet spintronics

  • Magnetic and thermodynamic models of iron-based alloys for fusion materials application
    Speaker
    Duc Nguyen-Manh
    United Kingdom Atomic Energy Authority
    United Kingdom
    Biography

    Duc Nguyen-Manh is the Principal Investigator of Eurofusion program and working at the Culham Centre for Fusion Energy (UKAEA). Currently his interest and expertise are focused in modeling and computational materials science from first-principles models of radiation-induced phase transformations in engineering components for nuclear fusion power plants. The foundation of his research is based on multi-scale modelling concepts linking materials science with physics, chemistry and engineering application in order to reduce uncertainties in predicting complex phenomena. This scheme allows having a new understanding on the origin of ordering and segregation in Fe-based alloys from magnetic interactions via development of the new magnetic bond-order potentials and magnetic cluster expansion method.

    Abstract

    Developing predictive models for magnetic ferritic and ferritic martensitic steels that exhibit higher resistance to irradiation than the other steels and using mathematical modelling as an exploratory tool for possible alternative compositions and microstructures, require formulating control approximations and simplified algorithms for large-scale computer simulations. In this talk, we review how computational methods based on first-principles calculations can elucidate several key properties of iron-based alloys, encompassing phase stability at high temperatures, chemical bonding as well as the structures of defects formed under irradiation. Our study is part of broader programme of work aiming of finding out how the properties vary as a result of exposure to fusion neutron irradiation. First-principles methods based on electronic structure calculations provide reliable information about microscopic phenomena the understanding of which is required for the development of large-scale models, such as efficient tight-binding based many-body Stoner Hamiltonian, magnetic cluster expansion and spin-lattice dynamic simulations. These innovative developments in modelling techniques and high-performance parallelized computer platforms, as well improved experimental characterisation tools, will certainly provide powerful means for developing self-consistent approaches for validating materials performance in fusion power-plant environments. Very recently, our models have been extended to the investigation of new class of iron-based magnetic high-entropy alloys which are the potential candidates for fusion materials application due high swelling resistance properties under irradiation at high temperature.

  • Process, Characterization and ESR Properties of 3d Transition Ion Doped-Tetrahedrite Compounds
    Speaker
    Cihat Boyraz
    Marmara University
    Turkey
    Biography

    Cihat Boyraz, Lecturer (Ph.D. physics), now is a Researcher in Marmara University, Faculty of Technology, Department of Mechanical Engineering. He got his B. Sc. in physics and Specialist in Magnetic and Superconductive materials. He got his Ph. D. at Marmara University department of physics. He worked in the research group of Prof. Dr. Arunava Gupta as a research scientist in Alabama State University. He also makes projects with Prof. Dr. Yildirhan Oner on superconductivity and magnetism. Dr. Boyraz’s magnetic superconductivity group has been working on Fe-based superconductors for 5 years.

    Abstract

    The increase in the usage of energy in the world brings an important global demand on finding new energy sources as either alternative or converting the waste energy for reuse. Among the types of waste energies, the heat energy plays an important role because of continuous wasting in our daily life from industry to our body heat. Due to the amount of waste heat is so high in daily life, the role of thermoelectricity topic in physics, which needs to be improved urges researcher to find alternative materials and to understand more on it. . Among the many sulphate salts, the group of tetrahedrite/tennatite has potential interest in physics in many ways are widely used in thermoelectric and photovoltaic applications. The importance of the thermoelectric researches is coming from neglecting the high material costs and long-termed synthesizing procedures. On the other hand, the properties of cheapness, accesibility, minimized risk factor in the usiage of thermoelectric materials make important for technological applications in scientific studies. Recently, tetrahedrite Cu12Sb4S13 material doped with different dopant elements exhibits important thermoelectric properties. Tetrahedrite, Cu12Sb4S13, is emerging as a promising phase in thermoelectrics. It exhibits an intrinsically low lattice thermal conductivity (?L = 0.4W m?1 K?1 at 700 K) due to unique features in its crystal structure. At the same time, the defect zinc-blende lattice ensures a good “crystalline” pathway for electron transport. At the same time, tetrahedrites are one of the most abundant TE minerals on Earth. In this study, main material Cu12Sb4S13 tetrahedrite doped with 3d ions such as Sb and As were synthesized using solid state reaction method. The annealing procedure was optimized for Sb and As doped -Cu12Sb4S13 tetrahedrite samples. Structural characterization was done by X-ray diffraction method (XRD). Scanning electron microscope (SEM) and an in-situ electron dispersive spectroscopy (EDS) were used for particle size and elemental compositions respectively. Electron spin resonance (EPR) and vibrating sample magnetometer (VSM) tools as shown in images also analyzed the compositions. Marmara University Bapko BAPKO under Project Fen-D-070617-0383 supported this work.

  • Magnetism in Pt-nanoparticles
    Speaker
    Roberto D’Agosta
    Universidad del Pais Vasco
    Spain
    Biography

    Roberto D’Agosta has completed his PhD in 2003 from University of Rome “Tre”. Then he moved to the University of Missouri-Columbia in the group of Prof. G. Vignale from 2003-2005 and then at the Physics Department, University of California – San Diego in the group of Prof. M. Di Ventra as research assistant since 2008. Dr D’Agosta moved to San Sebastian as visiting professor in Autumn 2008 and there he was offered a Ikerbasque Research Professorship starting in April 2009 at the University of the Basque Country (EHU/UPV), a position he holds at the moment. Although his research is mainly in the field of thermoelectric materials, thanks to a collaboration within the Thomas Young Centre (London) and then with Dr F. Baletto’s group at KCL, he brought his expertise in density functional theory to the study of magnetic materials.

    Abstract

    Nanoclusters are today of widespread use in various applications, ranging from nanomedicine to memory storage, nano-optics, plasmonics, and catalysis. Such a broad spectrum of applications is possible because of the delicate interplay between electronic structure and geometrical features in the absence of any translation symmetry, allows their peculiar and novel chemo-physical properties to be tunable by cluster architecture (size, shape, chemical composition and ordering) and by nanoparticles’ interaction with the surrounding environment. Unraveling the difficult shape-property relationship is indeed at the core of the so-called "bottom-up" approach. In the attempt of clarifying and exploiting the dependence of chemo-physical properties on cluster architecture, atomistic modeling based on density-functional theory offers a very powerful and detailed tool as we can manipulate and control nano-objects at the atomic scale in silico. In this talk, we are going to show how the magnetism arising in nano-sized Pt objects is due to a geometrical effect present in the second coordination shell and it is enhanced in twinned shapes. We also demonstrate how magnetism is affected by the environment in the case of small Pt-nanoclusters embedded in zeolite pores. Among the 50 stable isomers in the gas phase, due to geometrical constraints, only about 1/3 of those clusters can be inserted in the zeolite pores. Severe structural rearrangements occur depending on whether the solid angle at the Pt vertex bound to the super-cage, for example, the icosahedron reconstructs into a lower coordinated morphology. The high magnetic moment of Pt13 in a zeolite, is mainly due to four highly coordinated shapes -truncated bi-pyramid; a triaugmented triangular prism; two incomplete double icosahedra- which represent the 30% of the sample in the hypothesis that all the isomers have the same probability to be inserted in the pore

  • Effect of Cu substitution on the magnetism and electronic structure of hexagonal YMnO3
    Speaker
    Qi Li
    Southeast University
    China
    Biography

    Qi Li has completed his PhD in 1997 from National Synchrotron Radiation Laboratory, University of Science and Technology of China, and postdoctoral studies from Technical Physics Department, Peking University during Oct. 1997 to Aug. 1999, and from Physics Department, University of Leeds, United Kingdom, from Apr. 2001 to Apr. 2003. He has visited the Physics Department, University of Saskatchewan, Canada, from May 2007 to May 2008, as a visiting scholar. He is a professor of Physics at Southeast University, China. He has published more than 40 papers in reputed journals and has been serving as a reviewer of several repute journals

    Abstract

    YMnO3, a multiferroics, shows a low Neel temperature TN of about 75 K which hinders its practical applications. Thus, we doped Cu into it to improve its magnetism. All the YMn1-xCuxO3 samples crystallize into single phase of the hexagonal structure with P63 c m space group detected by XRD. The lattice parameter a increases while c decreases with increasing copper concentration, probably due to the difference in the ionic radii and the change of the hybridization between ions. The magnetic properties of YMn1-xCuxO3 samples are enhanced after doping Cu due to the deformation of the Mn trimer magnetic frustration arrangement and the double-exchange interaction between Mn3+ and Mn4+. The normalized O K-edge XAS spectra of YMn1-xCuxO3 show the hybridizations of O1s with Mn 3d/Mn 4sp and Y 4d/Y 5sp orbitals. With increasing Cu ions concentration, the intensity of e2g? peaks is enhanced indicating the enhancement of the orbital hybridization between Mn and OP. The in-plane hybridization strength enhances, leading to the decreases of Mn-OP bond length, in accordance with the XRD results. The normalized Mn L3,2-edge XAS spectra of the samples suggest the increase of the number of unoccupied Mn 3d states along the c-axis direction and the presence of Mn3+ and Mn4+ ions, causing double-exchange interactions and affecting the magnetic ordering of the frustrated Mn3+ spins.

  • Comparative study of structural, electrical and dielectric properties of Ni and Mg substituted Zn nano-ferrites
    Speaker
    Nasir Amin
    Government College University Faisalabad
    Pakistan
    Biography

    Nasir completed his M.Phil and Ph.D from Quaid-e-Azam University Islamabad, Pakistan in 1992 and 2007 respectively. He did his Post-doc from University of California San Deigo, USA in 2010. He has more than 15 years of research and teaching experience. Currently he is working as Chairman, Department of Physics and Dean of Science Faculty. He has published more than 30 research papers in International Journals with impact factor. He completed 5 research projects and 12 M.Phil students completed their degree under his supervision

    Abstract

    In this paper, we have reported the comparison of structural, optical and electrical properties for NixZn1-xFe2O4 and MgxZn1-xFe2O4 nano-particles. These nano-particles (x= 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared by co-precipitating aqueous solutions method using identical preparation conditions. The XRD patterns shows that both samples consisted of six peaks and related to (220), (311), (400), (422), (333), (440) planes of a cubic unit cell respectively and are in close agreement with characteristic peaks of soft ferrites. The particle size of MgxZn1-xFe2O4 was found to be decreasing from 31.32 to 19.55 nm by increasing magnesium content. While the particle size of NixZn1-xFe2O4 samples varied from 30.86 to 34.59 nm. The values of Lattice constant, volume, x-ray density, bulk density, particle size, porosity and dielectric constant, loss tangent and ac conductivity were also calculated for both series and results were compared. In conclusion our results suggested that MgxZn1-xFe2O4 can be a suitable replacement for NixZn1-xFe2O4 upto 3 MHz.

Young Researchers Forum
Chair
Co-Chair
  • Allied Academies Magnetic Materials 2017 Co-Chair Speaker Roman Boca  photo
    Roman Boca
    University of SS Cyril and Methodius in Trnava
    Slovakia
Speaker
  • Magneto-elastic effect on ferromagnetism induced by quantum-well states in Pd thin film
    Speaker
    Yusuke Ban
    Keio University
    Japan
    Biography

    Yusuke Ban is in 2nd grade of Master's course in Materials Science at Keio University, Japan.

    Abstract

    While Pd is a paramagnetic metal in bulk, a Pd(100) thin film shows ferromagnetism, which is dependent on the film thickness in an oscillatory manner. The appearance of ferromagnetism is attributed to the 4d electron quantum-well states. This suggests that the magnetism of Pd thin films can be switched through modification of quantum-well states due to change in the film thickness by introducing strain. In this work, the change in magnetism of epitaxial Pd thin layers in Pd (4.1 nm)/SrTiO3 (10nm)/BaTiO3 heterostructures, which is accompanied by deformation of BaTiO3, is studied using magnetization measurements and first-principles calculations. As shown in Fig. 1, BaTiO3 has four distinct temperature-dependent structural phases and the structural phase transitions can induce a large strain in the adjacent Pd layer. Fig. 2 shows clear changes in the magnetization of a Pd thin layer around the structural phase transition temperatures of BaTiO3. Such a change is mainly attributed to a variation in the Pd thickness, which intrinsically contributes to the appearance of ferromagnetism in Pd thin films, due to the stress from BaTiO3. As shown in Fig. 2, the observed magnetization change depends on temperature change process. This is due to the coexistence of two types of the ferroelastic domains, a-domain and c-domain, in BaTiO3; the strain effects on magnetism of Pd thin films are considered to be dependent on a ratio of these domains appeared at the interface, accordingly. The ratio changes from one phase transition to another, giving rise to an indeterministic change in magnetization as seen in Fig. 2. The magneto-elastic effect on magnetism originating from quantum-well states in Pd(100) thin film can be elucidated under voltage application to induce the formation of a single ferroelastic domain. Revealing the mechanism brings a new concept of electric-field control of magnetism.

  • Aspects of magnetocaloric effects and hyperthermia using magnetic materials
    Speaker
    Elena Yuan
    INCDIE-ICPE CA
    Romania
    Biography

    Elena Yuan is a Member of Excellency Centre for Young Olympics, part of (ICPE-CA)

    Abstract

    The paper presents the concerns of the authors about electromagnetic fields effect with potential applications in hyperthermia. Some theoretical aspects about using magnetosomes (magnetic nanoparticles found inside of Magnetotactic bacteria) in medical procedures in anticancer are commented. The next step is proposing a magnetic device that can also generate a thermal effect, the magnetic circuit having magnetic nanoparticles inside (case study magnetosomes) which powered at different frequencies can build a useful device in hyperthermia. Some projecting elements are presented, theoretical elements about thermodynamic involved, the behavior of magnetosomes introduced in tissues, and the arguments why magnetosomes can provide us with a solution are presented. Specific characteristics of magnetosomes and an obtaining technology are also presented.

  • The effect of alkali concentration on the structural and magnetic properties of Mn-ferrite nanoparticles prepared via the co-precipitation method
    Speaker
    Somayeh Pourbafarani
    Isfahan University
    Iran
    Biography

    Somayeh Pourbafarani her two essays were the result of her experimental work at university lab during her M.A study and self study after graduation. The subject of the aforementioned essay and also the way of observing and analyzing was an answer to all her questions which she had been involved in, while she hadn't found a clear and bright respond to them. She has received two awards from her government for her essays. She had also two presented papers. From the last publication, she has not done any research work, as she has not accessed any standard lab, and she has just focused on teaching. She accepted as a PhD student at one of Iranian University recently.

    Abstract

    Chemistry plays an important role in the development of novel nano-structural materials, and a simple control of solution chemistry can lead to specific changes in crystallite properties. One of the chemical techniques in the synthesis of nanoparticles is co-precipitation. The advantages of using this method are that the structural and morphological properties of nanoparticles can be varied by controlling the chemical and physical parameters of the reaction medium such as the alkali concentration, reaction temperature, molar ratio of salts, ionic strength of aqueous medium, and reaction time. In this work, MnFe2O4 nano particles were synthesized using the co-precipitation method under two different NaOH concentration settings as reaction agents at 355 K (82ºC). Structural and morphological properties of the nanoparticles were examined using X-ray diffraction and a scanning electron microscope. The decrease of NaOH concentration led to the increase of particle size, more crystallinity and a narrower particle size distribution. The results were evaluated from a chemical point of view and were based on the supersaturation level, which was in?uenced by alkali concentration. It was concluded that the higher NaOH concentration led to a more rapid nucleation and more random cation distribution. The magnetic properties of the nanoparticles were consistent with the structural and morphological properties of the particles.

  • Lock-in thermography: A new method for magnetic nanoparticles and the quantification of heat
    Speaker
    Federica Crippa
    University of Fribourg
    Switzerland
    Biography

    Federica Crippa studied Biomedical Engineering at Politecnico of Milan (2008-2013). She graduated in Biomechanics and Biomaterials with a thesis titled ‘Study of the AGEs effect on the mechanical properties of collagen fibrils through molecular models and experimental validation’ developed between Politecnico of Milan and ETH Zurich. Afterwards Federica worked as Assistant Researcher in the lab of Prof. Jess G. Snedeker at Uniklinik Balgrist in Zurich, focusing on proteins micromanipulations and surface modification analysis. From June 2014, she joined the Bio-Nanomaterials group at the Adolphe Merkle Institute as a PhD student under the supervision of Prof. Alke Fink and Prof. Barbara Rothen-Rutishauser. Her main field of research involves synthesis and characterization of magnetic nanoparticles for hyperthermia and mechanobiology.

    Abstract

    Magnetic nanoparticles (MNPs) and their ability to convert magnetic energy into heat are of explicit interest for several applications in biomedicine, in particular magnetic hyperthermia. The heating power of MNPs depends on their physico-chemical properties (e.g. size, colloidal stability and crystallinity) and external parameters such as magnetic field strength and frequency. However, precise evaluation of their heating power is non-trivial with conventional methods (e.g. fiberoptic cables, thermocouples and IR cameras) thus rendering comparative studies challenging. We propose a new method based on lock-in thermography to quantify the heating power of MNPs in a precise and reliable way. Nanoparticle suspensions are exposed to a modulated alternating magnetic field and their thermal signature is recorded with a synchronized IR camera. The signal is then processed and can be transformed into the heating slope. Lock-in based analysis of the heating properties of MNPs has been particularly useful to: 1) Quantify their heating power in suspension, semi-solid and aggregate states. In particular to screen the thermal properties of nanoparticles with different sizes, crystallinities, coatings and stability. 2) Investigate sources of variability and errors related to the alternating magnetic field (e.g. field strength inhomogeneity and its effects on the heating power). Overall, lock-in thermography is a new approach to precisely screen and analyze the heating power of different MNPs samples, facilitating comparative studies and the translation of these materials to the clinic.

  • Defect induced magnetism in ZnO: A first spintronic device application
    Speaker
    Lukas Botsch
    University of Leipzig
    Germany
    Biography

    Lukas Botsch has his interests in the field of magnetic materials and spintronic applications. During his Master in Physics, he studied Magnetic Semiconducting Oxides and their application in Optics and Spin Electronics. Working on his PhD, he is now studying defect-induced magnetism as a framework for semiconductor based spintronics

    Abstract

    The appearance of a magnetically ordered state in a nominally non-magnetic material through atomic lattice defects with a concentration of roughly five at. Percentage depends on the details of the lattice structure and the elements involved. The phenomenon Defect-Induced Magnetism (DIM) has been found in a broad spectrum of materials, like graphite, SiC and several oxides. The evidence for magnetic order obtained by different experimental methods like, e.g., Magnetization, XMCD, Electrical transport, EPR and NMR, leaves no doubt about its existence in solids. An interesting example of DIM in oxides is found in ZnO, a large gap semiconductor that has been thoroughly studied in the last ten years. DIM in pure ZnO can be induced by increasing the concentration of Zn vacancies through, e.g., proton irradiation. These defects can be stabilized in the ZnO lattice and remain above room temperature through previous doping with Li or Na, for example. The Curie temperature reached in this case remains always above 300K. In spite of a large amount of work, a possible application of DIM has not yet been realized. In this work, we present an electron-spin filter and a magnetoresistance sensor based on ZnO nanostructures, in which magnetic order was reached by introducing atomic lattice defects following the simple procedure to produce vacancies in ZnO through low-energy plasma treatment. The measured signals and the scalability of the phenomenon indicate a good potential of the observed phenomenon for applications in micro- and nanospintronics.

  • Computation of Neutral points in Magnetic Flux Density due to Magnets in Magnetic Motor for cogging reduction
    Speaker
    Amrit Panthi
    Tribhuvan University, Nepal
    Nepal
    Biography

    Amrit Panthi is final year students of Bachelor of Electrical Engineering, Pulchowk Campus, Institute of Engineering (IOE), Tribhuvan University (TU) . He has conducted a number of projects related to magnetism. He is interested on the reduction of cogging and harmonics in a permanent magnetic motor.On collaboration with National Academy of Science and Technology (NAST) and under the supervision of Professor Dr. Bhadra Prasad Pokharel he is conducting this research project.

    Abstract

    The magnetic field of the permanent magnet is analytically derived by using basic principles of the magnetism in very easier approach. The derived formula is easier in comparison to the methods that use Legendre polynomials, toroidal harmonics and hyper-geometric series. Concepts of origin shifting and geometrical shape transformation are used. Derivations are done in Cartesian co-ordinate system so that application becomes much easier and faster. This approach is equally applicable for the analysis of magnetic field distribution in space around for permanent magnet as well as electromagnet. Magnetic field visualization is also done for both magnitude and direction by using MATLAB. The idea of flux and field cancellation is used in order to visualize and locate the neutral points in order to reduce the effect of cogging in the permanent magnet motor.

Posters
Speaker
  • Magnetic phase diagram of spatially anisotropic frustrated two-dimensional antiferromagnet
    Speaker
    Vladimir Ilkovic
    Bogoliubov Laboratory of Theoretical Physics JINR
    Russia
    Biography

    Vladimir Ilkovic is working at Bogoliubov Laboratory of Theoretical Physics JINR, Russian Federation.

    Abstract

    The new magnetic materials such as the layered oxide high-temperature superconductor can be well described by the Heisenberg spin model with nearest-neighbor (NN) antiferromagnetic coupling J1 and next-nearest-neighbor (NNN) antiferromagnetic coupling J2. It is now well accepted that the model J1--J2 exhibits two phases displaying magnetic order at small J2, separated by an intermediate paramagnetic phase in the interval Jc1Jc1 it exhibits collinear stripe order. A generalization of the frustrated J1-J2 model is the J1x--J1y--J2 model where J1y is the directional anisotropy parameter. The nearest-neighbor bonds have different strength J1x and J1y in the x and y directions, respectively. The effect of the coupling J1y on the Neél and stripe states is investigated. Our aim here is to further the study of this model by using the quantum many-body Green function method. It has been applied successfully to calculate with high accuracy the properties of many lattice quantum spin systems.

E-Posters
Speaker
  • Low-temperature anomalies in thermal properties of YbB50 boride
    Speaker
    Nikolay A Zhemoedov
    Bryansk State University
    Russia
    Biography

    Nikolay A Zhemoedov has completed from Bryansk State University at the age of 22 years. Now he is is a Post-graduate student at Bryansk State University. The field of his scientific interest is low-temperature physics of crystals, which are perspective in modern areas of technology. His research is supported by a grant from the Russian Science Foundation (Project "Development of new thermoelectric materials based on clathrates and clathrate-like substances", No. 16-12-00004, 2016-2018). He took part in some International conferences on the physics and chemistry of borides. He has four publications in reputed journals that have been cited 7 times and two presentations on international conferences. His h-index is two.

    Abstract

    Heat capacity and thermal expansion of YbB50 boride have been studied at 2-300 K. The sharp anomaly at about 5 K and smooth humps of the studied properties of boride at elevated temperatures was detected. The excess heat capacity and abnormal contribution to the thermal expansion of YbB50 have been determined by comparison with a paramagnetic LuB50 compound. Low-temperature anomalies of YbB50 thermal characteristics have been attributed to the magnetic phase transition to the antiferromagnetic state. The anomalies at 50-150 K temperature region were satisfactory described as results of the ground level splitting by the crystal an electric field (CEF). The scheme of CEF splitting was proposed.

  • Application of static magnetic field for alleviation of adverse effects of salt stress on germination and early growth characteristics in maize and soybean
    Speaker
    Sunita Kataria
    Shri Vaishnav Vidyapeeth Vishwavidyalaya
    India
    Biography

    Sunita Kataria has completed her Ph.D. in 1999 from School of Life Sciences, Devi Ahilya University and Postdoctoral studies from School of Life Sciences, Devi Ahilya University. She has 15 years of research experience and worked as CSIR Research associate, CSIR Pool Scientists and DST-Women Scientists in School of Life Sciences, DAVV, Indore. She has published more than 40 papers in reputed journals and 03 book chapters.

    Abstract

    Maize and Soybean seeds were pre-treated with static magnetic field (SMF) of 200 mT for 1 h to evaluate the effect of static magnetic field for alleviation of adverse effects of salt stress on germination and early growth characteristics. The adverse effect of NaCl induced salt stress was found on percentage germination and germination related parameters. Enhanced percentage germination and early seedling growth parameters (root and shoot length, and vigour indices) under different salinity levels (0 to 100 mM NaCl) indicated that magneto priming was more effective in alleviating salinity stress at early seedling stage of both maize and soybean as compared to untreated seeds. ?- amylase and protease activities were also higher in SMF treated seeds under both non-saline and saline conditions. This could have resulted in faster hydration of enzymes in SMF treated seeds leading to higher rate of germination. Increased levels of superoxide radical and hydrogen peroxide was found in germinating magnetoprimed seeds of maize and soybean, under both the growing conditions. Enhancement in seed germination and seedling vigour under both the growing conditions by SMF treatment may be due to the combined effect of enhanced ?- amylase and protease activities and enhanced levels of free radicals in the seeds. Consequently, SMF pre-treatment effectively mitigated adverse effects of NaCl on both maize and soybean.

  • Synthesis, structural and electrical characterization of soft Ni-Cr nanoferrites
    Speaker
    Asghari Maqsood
    Air University
    Pakistan
    Biography

    Asghari Maqsood has her expertise in the fabrication and characterization of new materials. She prepared single crystals of rare-earth disilicates with the formula R2 Si2O7 (R=Tm, Er, Ho, Dy). These materials were characterized through X-diffraction, magnetic, electrical and dielectric measurements. The results appeared in the ISI indexed journals, indicating the structural and importance of these materials from the application and academic interest. She also has the experience of dealing with high-temperature superconductors, thin-films of groups II-VI semiconductors and their application in solar cell technology. She developed a research laboratory namely Thermal Physics at Quaid-i-Azam University for post graduates, leading to MPhil and PhD degrees. The research group got involved in the synthesis of nanoferrites and their characterization almost a decade ago. The researchers have completed their research projects related to soft and hard nanoferrites for their PhD’s under her supervision. The materials showed their applications in electronics, utility at high frequency, mechanical stiffness, etc. The systems CoFe2O4, Cu/Cd doped Mg-Zn; Cd doped Ni- ferrites are studied at length and the results are reported in publications.

    Abstract

    Ferrites which are ferrimagnetic ceramic materials have different metal oxides converged with iron (Fe3+) to form their core segment. Ferrites are of two kinds, soft and hard. Soft materials are used for electromagnets because they are simply magnetized and demagnetized. On the other hand, hard materials are hard to magnetize and demagnetize, so they are used for permanent magnets. The core properties of ferrites depend on composition, synthesis techniques, temperature, cation distribution and the particle size. Although iron and metallic alloys are scientifically useful as magnetic materials, these materials are impractical because of low resistivity at high frequency. Because of high electrical resistivity of these ferrites, these are superior at high frequencies. In this talk, the fabrication of Cr doped Ni0.5-Zn0.5CrxFe2-xO4 (0.1?x?0.4) is reported. The material was characterized by x-ray diffraction technique to get the information related to structure, average crystallite size, x-ray density, porosity, the specific surface area and surface to volume ratio as shown in the Fig. The variation of electrical parameters like DC electrical resistivity and mobility as a function of temperature was investigated in the range of 435 to 770 K. The activation energies of all the samples were calculated from the DC electrical resistivity data. The dielectric parameters such as dielectric constant ( ), dielectric loss (tan?) and AC conductivity (?ac) are measured in the temperature range of 300 to 770 K. It was observed that the dielectric constant was found to increase with the Cr3+ concentration, while tan? and ?ac decreased. The results are explained on the basis of increase in interfacial and dipolar polarization in the samples. Transition temperatures obtained from dielectric constant are in agreement with Curie temperatures, obtained from resistivity plots.

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