A5091664699- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Magnetic Properties of Alloys
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Magnetic Properties and Applications
- Multiferroics and related materials
- Electronic and Structural Properties of Oxides
- Heusler alloys: electronic and magnetic properties
- Surface and Thin Film Phenomena
- Theoretical and Computational Physics
- Topological Materials and Phenomena
- Advanced Materials Characterization Techniques
- nanoparticles nucleation surface interactions
- Microstructure and Mechanical Properties of Steels
- Semiconductor materials and devices
- Iron-based superconductors research
- 2D Materials and Applications
- Superconductivity in MgB2 and Alloys
- Thermal Expansion and Ionic Conductivity
- Graphene research and applications
- High Temperature Alloys and Creep
- Boron and Carbon Nanomaterials Research
University of Nebraska–Lincoln
2016-2025
Far Eastern Federal University
2016
Tohoku University
2016
Johns Hopkins University
2016
Ames National Laboratory
2001-2015
United States Department of Energy
2015
Lawrence Livermore National Laboratory
2015
Iowa State University
2001-2015
University of California, Santa Barbara
2014
Kurchatov Institute
1996-2000
Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at Fermi level derive mainly from B orbitals. Strong bonding an ionic component considerable metallic density states yield sizable electron-phonon coupling. Together high phonon frequencies, which we estimate via zone-center frozen to be between 300 700 cm(-1), this produces critical temperature, consistent recent experiments....
Advances in scaling down heterostructures and having an improved interface quality together with atomically thin two-dimensional materials suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or enhanced spin–orbit coupling. Such not only complement the conventional methods designing by doping...
Based on first-principles calculations, we demonstrate the impact of electric polarization electron transport in ferroelectric tunnel junctions (FTJs). Using a Pt/BaTiO3/Pt FTJ as model system, show that BaTiO3 barrier leads to substantial drop tunneling conductance due changes electronic structure driven by displacements. We find sizable change transmission probability across Pt/BaTiO3 interface with reversal, signature electroresistance effect. These results reveal exciting prospects FTJs...
Symmetry arguments are used to show that a boundary of magnetoelectric antiferromagnet has an equilibrium magnetization. This magnetization is coupled the bulk antiferromagnetic order parameter and can be switched along with it by combination E B fields. As result, domain state as nonvolatile switchable variable in nanoelectronic device applications. Mechanisms affecting its temperature dependence classified. The especially large if breaks equivalence sublattices.
This paper summarises the theory and functionality behind Questaal, an open-source suite of codes for calculating electronic structure related properties materials from first principles. The formalism linearised muffin-tin orbital (LMTO) method is revisited in detail developed further by introduction short-ranged tight-binding basis functions full-potential calculations. LMTO presented both Green's function wave formulations bulk layered systems. suite's code uses a sophisticated...
Electrostatic gating enables key functionality in modern electronic devices by altering the properties of materials. While classical electrostatics is usually sufficient to understand effects extended systems, inherent quantum nanostructures offer unexplored opportunities for materials and devices. Using first-principles calculations Co/bilayer graphene, Co/BN/graphene, Co/BN/benzene, as well a simple physical model, we show that heterostructures with two-dimensional yield tunable magnetic...
Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets separated by a nonmagnetic insulating layer are key building blocks in spintronics for magnetic sensors and memory. A radically different approach of using atomically-thin van der Waals (vdW) materials MTJs is expected to boost their figure merit, the tunneling magnetoresistance (TMR), while relaxing lattice-matching requirements from epitaxial growth supporting high-quality integration dissimilar atomically-sharp...
Abstract Twistronics, a novel engineering approach involving the alignment of van der Waals (vdW) integrated two‐dimensional materials at specific angles, has recently attracted significant attention. Novel nontrivial phenomena have been demonstrated in twisted vdW junctions (the so‐called magic angle), such as unconventional superconductivity, topological phases, and magnetism. However, there only few reports on layers with large twist angles θ t , interfacial Josephson using...
Chemical bonding and electronic structure of ${\mathrm{MgB}}_{2},$ a boron-based newly discovered superconductor, is studied using self-consistent band-structure techniques. Analysis the transformation band for hypothetical series graphite--primitive graphitelike boron--intercalated boron, shows that ${\mathrm{MgB}}_{2}$ graphitelike, with \ensuremath{\pi} bands falling deeper than in ordinary graphite. These possess typically delocalized metallic, as opposed to covalent, character. The...
The electronic structure and spin-dependent tunneling in epitaxial $\mathrm{Fe}∕\mathrm{Mg}\mathrm{O}∕\mathrm{Fe}(001)$ tunnel junctions are studied using first-principles calculations. For small MgO barrier thickness the minority-spin resonant bands at two interfaces make a significant contribution to conductance for antiparallel magnetization, whereas these are, practice, mismatched by disorder and/or applied bias parallel magnetization. This explains experimentally observed decrease...
Recent experimental and theoretical studies of the magnetoelectric (ME) effect in nanocomposite structures laminates show an enhanced ME coefficient. These materials combine piezoelectric properties paramagnetic phase piezomagnetic magnetic phase. We propose to fabricate heterostructures formed by antiperovskites as materials. that structure antiperovskite, such ${\mathrm{Mn}}_{3}\mathrm{Ga}\mathrm{N}$, can be controlled a small applied biaxial strain. The lowering symmetry with strain...
We report the direct observation of surface magnetization domains magnetoelectric Cr(2)O(3) using photoemission electron microscopy with magnetic circular dichroism contrast and force microscopy. The domain pattern is strongly affected by applied electric field conditions. Zero-field cooling results in an equal representation two types, while electric-field selects one dominant type. These observations confirm existence magnetization, required symmetry antiferromagnets.
The electronic structure and magnetism of chromia (corundum-type ${\text{Cr}}_{2}{\text{O}}_{3}$) are studied using full-potential first-principles calculations. correlations included within the $\text{LSDA}+U$ method. energies different magnetic configurations very well fitted by Heisenberg Hamiltonian with strong exchange interaction two nearest neighbors additional weak up to fifth neighbor shell. These insensitive position oxygen states, indicating that in ${\text{Cr}}_{2}{\text{O}}_{3}$...
The electronic structure and magnetic properties of pure doped Fe${}_{16}$N${}_{2}$ systems have been studied in the local-density (LDA) quasiparticle self-consistent $\mathit{GW}$ approximations. moment is somewhat larger compared to LDA but not anomalously large. effects doping on exchange coupling were analyzed using coherent potential approximation. Our lowest estimate Curie temperature significantly higher than measured value, which we mainly attribute quality available samples...
Recently there has been substantial interest in realizations of skyrmions, particular quasi-two-dimensional (2D) systems due to increased stability resulting from reduced dimensionality. A stable skyrmion, representing the smallest realizable magnetic texture, could be an ideal element for ultradense memories. Here we use most general form quasi-2D free energy with Dzyaloshinskii-Moriya interactions constructed symmetry considerations reflecting underlying system. We predict that skyrmion...
Spintronic structures are extensively investigated for their spin–orbit torque properties, required magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering optimization of spin transmission. Here, we advance analysis ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to inverse spin-Hall effect properties. In particular, intrinsic Pt-based systems and extrinsic Au:W Au:Ta NiFe/Au:(W,Ta)...
We perform an ab initio study of spin-polarized tunneling in epitaxial Co/SrTiO(3)/Co magnetic tunnel junctions with bcc Co(001) electrodes. predict a large magnetoresistance these junctions, originating from mismatch the majority- and minority-spin bands both bulk Co at interface. The intricate complex band structure SrTiO(3) enables efficient minority d electrons which causes spin polarization interface to be negative agreement experimental data. Our results indicate that electrodes are...
Fully relativistic first-principles calculations of the Fe(001) surface demonstrate that resonant (interface) states may produce sizable tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a single electrode. The effect is driven by spin-orbit coupling. It shifts band via Rashba when magnetization direction changes. We find spin-flip scattering at interface controlled not only strength coupling, but depends strongly on intrinsic width states.
First-principles calculations based on density functional theory are used to elucidate the effect of O vacancies, forming F centers, spin-dependent tunneling in Fe∕MgO∕Fe(001) magnetic tunnel junctions. vacancies produce occupied localized s states and unoccupied resonant p states, which is consistent with available experimental data. The authors find that affect conductance by nonresonant scattering electrons causing a substantial reduction magnetoresistance (TMR). Improving quality MgO...
A minority-spin resonant state at the $\mathrm{Fe}/\mathrm{GaAs}(001)$ interface is predicted to reverse spin polarization with voltage bias of electrons transmitted across this interface. Using a Green's function approach within local spin-density approximation, we calculate spin-dependent current in $\mathrm{Fe}/\mathrm{GaAs}/\mathrm{Cu}$ tunnel junction as applied voltage. We find change sign tunneling due resonance. This result explains recent experimental data on injection...
First-principles calculations are used to explore the possibility of enhancing N\'eel temperature ${T}_{N}$ magnetoelectric antiferromagnet Cr${}_{2}$O${}_{3}$ by substitutional doping. We describe electronic structure transition metal (V, Ti, Mn, Fe, Co, and Ni) anion (N B) impurities evaluate their effect on exchange interaction. find that, although transition-metal N likely reduce ${T}_{N}$, substitution O B is increase it. Both introduce impurity states mediating strong hybridization...