It is noteworthy that the tunneling magneroresistance TMR ratio is higher for symmetric junctions rather than non-symmetric junctions. These results indicate that the bilayer sheets of graphene and h-BN are promising candidates for the spacer of magnetroresistive junctions in the application of spintronics.
Tomoya Ono was born in Okayama, Japan, in D from Osaka University. His current research interests include the design and simulation of quantum transport and the development of new computational methods for first-principles calculations. Abstract The geomagnetic field provides all animals that can sense it with a wealth of navigational information. This is best studied in birds: they can use the direction of the geomagnetic field as a compass and components like intensity as a part of their navigational map.
The magnetic compass was analyzed based on the orientation of the spontaneous activity of migratory birds, an analysis that revealed some surprising characteristics: 1 The avian magnetic compass functions only in a biological windows around the intensity of the local magnetic field.
This window is flexible, however; birds can oriented in intensities outside if they have been exposed to these intensities before. Observations are in agreement with this model: orientation is disrupted by RF-fields, and cryptochrome 1a is found in the outer segments of the UV cones in the retina of birds.
Birds are also able to record the intensity of the geomagnetic field and use it as a component of the map mechanism determining position. The receptor mechanisms for this sense are still poorly known; they seem to involve in magnetite-based receptors in the beak. Their joint research focused on the avian magnetic compass, its functional mode, biological significance and possible reception mechanisms as well as bird navigation.
Abstract Magnetic skyrmions are topologically protected whirling spin texture. Their nanoscale dimensions, topologically protected stability and solitonic nature, together are promising for future spintronics applications. To translate these compelling features into practical spintronic devices, a key challenge lies in achieving effective control of skyrmion properties, such as size, density and thermodynamic stability.
Moreover, by manipulating the ferroelectric polarization of the BaTiO3 layer, we achieve local, switchable and nonvolatile control of both skyrmion density and thermodynamic stability. This ferroelectrically tunable skyrmion system can simultaneously enhance the integratability and addressability of skyrmion-based functional devices. He has published more than 20 papers in reputed journals. Abstract As the nearest-row neighbor of carbon, boron have similar structural features and rich electronic properties when forming nanostructures.
In this talk, we will show that boron and boron-carbon nanostructures exhibit rich variety of electronic properties. We show that BCS superconductivity in the stable 2D boron structures is ubiquitous with the critical temperature above the liquid hydrogen temperature for certain configurations.
Our results support that 2D boron structure may be a pure single-element material with the highest Tc on conditions without high pressure and external strain. Our results reveal that the lower-frequency acoustic branch affected by the strain plays an important role for the variation of the superconductivity. Our results show that the adsorption energy of alkaline and alkaline earth atoms on BC3 sheet is larger than the cohesive energy of the metal atoms themselves.
We show that, under a suitable external electric field, a considerable magnetism can be induced, accompanying with the emergence of both magnetism the electric dipole moment of the systems with strong coupling of them. The thallium Tl decorated BC3 and the transition metal atoms adsorbed BC3 can host robust quantum spin Hall state and quantum anomalous Hall state, respectively, which indicates that the systems of graphenelike BC3 with adatoms are good platforms for the study of quantum spin Hall and quantum anomalous Hall effects.
He is now the professor in Department of Physics, Tsinghua University. He has published more than papers in reputed journals. Abstract The aimed of this work was to synthesize magnetic nanoparticles Fe3O4, NiFe2O4 and NiFe2O4 , prepared as nanofluids, thin films and nanocomposites, using several techniques of preparation such as coprecipitation, hydrothermal and sol-gel processes. The variation in the processing resulted in different materials with regards to physical-chemistry properties, which were confirmed by characterization techniques during the processes.
The materials have been characterized by X-ray diffraction, infrared spectroscopy, gas adsorption, scanning electron microscopy, high resolution transmission electron microscopy, electron diffraction, EDS and EELS. The magnetic properties of materials have been studied as a function of the preparation temperature and used process. The obtained materials were tested in several application such as production of ink, catalyst, cancer treatment, ferroic devices, among others.
She supervised directly various undergraduate and graduate students. She has experience in the field of material science, with emphasis on physics and chemistry of the condensed state, acting mainly in the following themes: Nanoscience and nanotechnology, coprecipitation, hydrothermal and sol-gel processes.
She works with the synthesis, characterization and application of nanoparticle materials, nanocomposites, ferrofluids and thin films. She has large experience in coordination of several academic projects, including projects in collaboration with Brazilian companies. Abstract A magnetic proximity effect of a topological insulator in contact with an itinerant ferromagnet in thin film bilayers of Bi0.
I shall also discuss the observation of strongly suppressed superconductive proximity effect and ferromagnetism in topological insulator, ferromagnet and superconductor thin film trilayers of Bi2Se3 on SrRuO3 on underdoped YBa2Cu3Oy . By comparing our transport and magnetoresistance results of the bilayers and trilayers to those of a reference ferromagnetic film, and a reference trilayer with the topological layer replaced by a highly overdoped and non-superconducting La1.
While a conventional proximity effect was found in the bilayers, in the trilayers proximity induced edge currents led to the creation of a 2D network of 1D channels of weak-link superconductivity on the wafer. Conductance spectra of micro-bridges pattern on these trilayers reveal zero bias conductance peaks which are sensitive to magnetic field and could be attributed to Majorana zero energy bound states.
Though our trilayer network of weak-link channels is disordered, it is similar in concept to that of the artificially prepared ordered network demonstrated in the literature by growing selectively Al on InAs . Both systems could provide a platform for future Majorana electronics for quantum computing.
His fields of interest in condensed matter physics and laser applications include high temperature superconductivity, proximity effects and magnetism using epitaxial thin films, junctions and multilayers with various ferromagnets, topological insulators and normal metals. Abstract Exploring single phase multiferroic materials has been a long-time-sought quest due to the promise of novel spintronic devices.
BiFeO3 has been recognized as the most important room temperature single phase multiferroic material which has a large polarization together with the antiferromagnetism above room temperature. However, the weak magnetoelectric coupling remains as the key issue which obstructs its applications. On the other hand, type-II multiferroics, where the ferroelectricity generally originates from some special magnetic structure, have the serious shortcomings of very weak polarization and a critical temperature much lower than room temperature though a strong magnetoelectric coupling is expected.
In the present work, both BiFeO3—based solid solutions and h-RFeO3 multiferroic new systems are systematically investigated. Electric field-controlled magnetism is achieved in Bi1-xRxFeO3 solid solutions by tuning the symmetry from polar R3c to polar Pna21, where two morphotropic phase boundaries MPB are detected together with the greatly enhanced ferroelectric polarization and magnetism.
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The electric field-controlled magnetism is realized by an electric field induced structural and magnetic transition from Pna21 back to R3c, and this transition is shown to be reversible with additional thermal treatment. On the other hand, h-RFeO3 room temperature single phase multiferoic new materials have been designed and created by introducing chemical pressure In-substitution for Lu in LuFeO3. Abstract Spinel oxide materials are characterized by an AB2O4 structure, where A and B are divalent and trivalent cations.
The A cations occupy the tetrahedral positions Th in the structure, whereas the B cations occupy the octahedral Oh ones. If some degree of inversion, x, exists, the structure is represented as A1-xBx [AxB2-x]O4, where denote Th positions in the structure and [ ]Oh positions, respectively. The evaluation of the inversion parameter, x, in spinel materials is crucial to understand their functional magnetic properties. For large volume materials, several techniques such as x-rayand neutron diffraction refinement, Mossbauer spectroscopy, x-ray absorption or nuclear magnetic resonance are extensively used to assess the coordination of chemical species.
In this work, using scanning transmission electron microscopy and electron energy loss spectroscopy STEM-EELS , two different methods to calculate the cation inversion parameter of spinel crystals with unprecedented spatial resolution are demonstrated. The first one is based in the measurements of energy loss near edge spectroscopy ELNES features, to evaluate the oxidation state of transition metals by using the onset of the L3 peak.
II-Materials and Applications
An alternative way is to apply multivariate analysis MVA and spectral decomposition techniques to map the contribution of divalent and trivalent components. Interestingly, X-ray absorption experiments, a well-stablished method to asses cation coordination inversion on the nanoparticle powder samples confirm the presence of cation inversion in Mn3O4 with reasonably similar values.
The main objective of LENS is the development of instrumental methods as well as data treatment for advanced scientific problems in nanomaterials usingTEM techniques. Abstract Barium hexaferrite HF nanoplatelets display a high uniaxial magnetocrystalline anisotropy with an easy axis that is perpendicular to the platelet. This unique property gives them tremendous potential in innovative applications, for example, in the magneto-mechanical eradication of cancer cells.
As the nanoplatelets adopt a distinct structure and composition, which are significantly different to the bulk, they can be considered as novel structural variations of hexaferrite stabilized on the nanoscale. The weak point of the HF nanoplatelets is their modest saturation magnetization, MS. The increase was unexpected as the Sc-substitution decreases the MS of the bulk. In the lecture this opposite effect of the Sc-substitution in the nanoplatelets than in the bulk will be discussed based on combination of detailed analysis of the lattice site of Sc incorporation and ab-initio calculations.
He has defended his PhD from chemistry at the University of Ljubljana in year His scientific interests are focused in synthesis and characterization of the inorganic and hybrid nanomaterials, especially materials containing magnetic nanoparticles. He is also expert in advanced electron microscopy. Prof Makovec has published over peer-review articles. To achieve high coercivity, remanence and consequently high energy product at elevated temperatures the addition of heavy rare earth HRE to the basic Nd-Fe-B composition] is needed.
To drastically reduce the use of HRE we focused on developing a new method, which should enable us to achieve the properties needed for high-temperature application with the lowest amount of scarce elements. By our new inventive technique further transferred to a pilot production, we could minimize the amount of HRE used, down to 0.
The total saving of the HRE is times less need for the same performance, which is a significant contribution to the world economy and clean environment.
Magnetic 2D materials and heterostructures
In studying the mechanism for such an improvement in coercivity without significantly decreasing the remanence, a detailed microstructure investigation was performed by using high-resolution transmission electron microscopy. Besides the use of these new developed high energy magnets for electric and hybrid cars and the wind turbine generators the important application is also as the source of the magnetic field in the development of the new magnetic cooling devices.
Abstract Ferromagnetic materials with large magnetostriction have found wide applications in sensors, transducers and actuators based on the conversion between magnetic and elastic energies. Fe-Ga solid solutions, known for the large magnetostriction at low external fields and the good mechanical property, have attracted considerable interest since The structural diversity of Fe-Ga alloys allows one to obtain abundant properties from the composites containing two or more phases.
The slow transformation kinetics, different intrinsic magnetic properties and elastic properties of these two phases can facilitate novel properties that are highly desired in engineering applications. The gradual transformation from the BCC phase with lower magnetization into the FCC phase with higher magnetization can facilitate highly thermal stable magnetization up to K [Nature Comm. The compensation of stress-induced anisotropies between these two phases with opposite magnetostriction signs can facilitate highly stable magnetic permeability under stresses [PR Mater.
Our work suggests that controlling the diffusional phase transformation is a useful tool to design multi-functional ferromagnetic materials. His research interest covers functional magnetic materials and rare earth permanent magnets. He has published more than papers in peer-reviewed journals, such as Nature Communations, Acta Materialia, Physical Review Materials, etc. Abstract By method of pulsed electron beam evaporation in vacuum of targets from non-magnetic in bulk state, Al2O3, SiO2, CeO2, CaF2 and BaF2 magnetic nanopowders with a high specific surface were produced.
The nanopowders were irradiated in air in room-temperature by electrons with energy of 0. The magnetic, thermal, and cathodoluminescence characteristics of nanopowders were measured before and after irradiation. It was established that the electron irradiation non-monotonically changes the magnetization of the pristine samples. To the contrary, a clear correlation between the intensity of cathodoluminescence and the irradiation does is found in the most of the oxides and fluorides.
There was a decrease in the intensity of cathodoluminescence after irradiation. Thermal stability and phase transformations of unirradiated and irradiated nanopowders were analyzed by synchronous analysis using thermogravimetry and differential scanning calorimetry.
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Luminescent and thermal properties reflect the transformation of structural defects in nanopowders more strongly after the exposure to a pulsed electron beam in comparison with corresponding changes of the nanopowders magnetic response. He developed a method for production of nanopowders, including evaporation of a target by a pulsed electron beam, condensation of the vapor of the material in a low-pressure gas, and deposition of nanopowders on a large cold square crystallizer.
Abstract The Kitaev model is a promising way to realize a topological quantum spin liquid, which would be suitable for quantum computing. This ordered state can be suppressed under magnetic fields toward a field-induced quantum spin liquid. Magnetization measurements under hydrostatic pressure revealed a pressure-induced structural transition into a non magnetic state : a valence bond crystal with the formation of Ru-Ru bonds . The ground state of Ru1-xCrxCl3 was found to be a spin glass on a broad Cr concentration range.
He is now post doctorant at the IFW-Dresden. Abstract Magnetic skyrmions are topologically stable whirlpool-like spin textures that offer great promise as information carriers for future ultra-dense memory and logic devices. To enable such applications, particular attention has been focused on the skyrmions in highly confined geometry such as nanodisks or one dimensional nanostripes or wires.
Here, we systematically reviewed our recent effort on the real space visualization and manipulation of individual magnetic skyrmion in FeGe nanostripes or nanodisks by high resolution Lorentz transmission electron microscopy TEM and electron holography technique. We observed the flexibility of the shape of individual skyrmion tuned by the width and a unique field-driven helix-to-skyrmion cluster states transition directly.
Also, a new state, called target skyrmion consisting of a central skyrmion surrounded by one or more concentric helical stripes and the magnetic bobbers are also identified. These findings demonstrate that the geometry defects can be used to control the formation of topologically nontrivial magnetic objects. He has published more than papers in reputed journals and has been serving as the Advisory Editorial Board member for the Journal of Magnetism and Magnetic Materials.
Abstract In polyacetylene and graphene nanoribbons a solition with a fractional charge exists as a domain wall connecting two different phases. In polyacetylene a fermion mass potential in the Dirac equation produces an excitation gap, and a twist in this scalar potential produces a zero energy soliton.
Similarly, in gapful graphene nanoribbons a distortion in the chiral gauge field can produce a solitonic domain wall between two neighboring zigzag edges with different chiralities . The existence of a soliton in polyacetylene can lead to formation fractional charges on the opposite ends of polyacetylene. However, the situation is different in graphene nanoribbons with an excitation gap since antiferromagnetic coupling between the opposite zigzag edges shown in Fig. We show that presence of disorder in graphene nanoribbons partly mitigates the effect of antiferromagnetic coupling between the opposite zigzag edges, see Fig.
As a consequence of this, midgap states can have fractional charges on the opposite zigzag edges in the weak disorder regime . The probability density of such a state is shown in Fig. The measurement of the differential conductance in atomically precise graphene zigzag nanoribbons  using a scanning tunneling microscopy may provide rich information on the distribution of edge charges.
References  Y. Jeong, S. Kim and S. Eric Yang, Topological gap states of semiconducting armchair graphene ribbons, Phys. B 91, Jeong and S. Eric Yang, Topological end and Zak phase states of rectangular armchair ribbon, Annals of Physics , Eric Yang, and M. Cha, Fractional edge charges of interacting disordered graphene zigzag nanoribbon, arXiv Ruffieux, S. Wang , B. Yang , C. Sanchez-Sanchez , J. Liu, T. Dienel, L. Talirz , P. Shinde, C. Pignedoli, D. Passerone, T. Dumslaff , X.
Feng, K. Mullen and G. Fasel R, On-surface synthesis of graphene nanoribbons with zigzag edge topology, Nature , Professor S. He is a condensed matter theorist. His long-time interest has been the interplay between disorder and elecron interaction. Abstract Zinc Oxide is a semiconductor which used in electronic devices due to its physical and its chemical bonds properties, where these chemical bonds is between ionic and covalent.
The short-range of interatomic interaction is modeled by a pair potential of Buchingham and the long-range by the Coulomb interaction. Our results are in vicinity of theoritical and experimental lierature although no more work under previous conditions of extended temperature and pressure. These data is very important in industry of technology and nanotechnology especialy in geophysics, medecine, pharmacetics , and cosmetics.
Our results are a simulation prediction which need confirmation in future.
He is a teacher in Boumerdes University since He has published more than 7 papers in reputed journals and has been serving as a referee with condensed matter journal IOP and Energy journal Elsevier. He passed 6 months in Cardiff University and Queen University for summer school. Abstract Nowadays, energy-saving and increasing the efficiency of power transmission lines, electrical machines and transformers are important as much as diversity and renewability of energy resources. The existing worldwide power transmission lines are sufficient for 1GW power transmission, which meets the current need of the World.
However, considering the increasing power need it would be impossible to transmit dozens of GW power using the existing transmission lines due to the current carrying limitation of the metals used in transmission lines. Hence, it is necessary to develop new materials for power transmission lines. Although superconductors are a superior choice in terms of energy efficiency, it has disadvantages such as high production and operation costs in addition to critical temperature, current and field limitations. The production stages of superconductor wires are performed by using special devices and expensive techniques.
Moreover, cooling them down to cryogenic temperatures increases the operating costs. Thus, superconductors are not used in power transmission except a few test-based applications in the World. Please note, students who have not taken the prerequisites listed above must have taken an equivalent version of Thermodynamics and Solid State II and Mathematics II.
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