A5023843825- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Surface and Thin Film Phenomena
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Magnetic and transport properties of perovskites and related materials
- ZnO doping and properties
- Heusler alloys: electronic and magnetic properties
- Theoretical and Computational Physics
- Rare-earth and actinide compounds
- Magnetic Properties and Applications
- nanoparticles nucleation surface interactions
- Metallurgical and Alloy Processes
- Intermetallics and Advanced Alloy Properties
- Semiconductor materials and interfaces
- Electronic and Structural Properties of Oxides
- Magnetic Properties of Alloys
- Chemical and Physical Properties of Materials
- Electron and X-Ray Spectroscopy Techniques
- Chalcogenide Semiconductor Thin Films
- Advanced Materials Characterization Techniques
- Thermodynamic and Structural Properties of Metals and Alloys
- Shape Memory Alloy Transformations
- Advanced Physical and Chemical Molecular Interactions
- Advanced Thermoelectric Materials and Devices
Czech Academy of Sciences, Institute of Physics
2012-2022
Czech Academy of Sciences
2012-2022
Czech Academy of Sciences, Institute of Physics of Materials
2015-2020
Czech Academy of Sciences, Institute of Plasma Physics
2006-2019
Institute of Physics of the Slovak Academy of Sciences
1988-2014
University of Nebraska–Lincoln
2012
Max Planck Institute of Microstructure Physics
2000-2009
University of Vienna
1993-2007
Institut Laue-Langevin
2003-2005
TU Wien
1967-2004
This review summarizes recent first-principles investigations of the electronic structure and magnetism dilute magnetic semiconductors (DMSs), which are interesting for applications in spintronics. Details transition-metal-doped III-V II-VI described, especially how couples to properties an impurity. In addition, underlying mechanism ferromagnetism DMSs is investigated from point view order establish a unified picture that explains chemical trend DMSs. Recent efforts fabricate high-${T}_{C}$...
We have calculated Heisenberg exchange parameters for bcc Fe, fcc Co, and Ni using the nonrelativistic spin-polarized Green-function technique within tight-binding linear muffin-tin orbital method by employing magnetic force theorem to calculate total energy changes associated with a local rotation of magnetization directions. also determined spin-wave stiffness constants found dispersion curves metals in question Fourier transform parameters. Detailed analysis convergence properties...
Effective pair exchange interactions between Mn atoms in III-V and group-IV diluted magnetic semiconductors are determined from a two-step first-principles procedure. In the first step, self-consistent electronic structure of system is calculated for collinear spin at zero temperature with substitutional disorder treated within framework coherent-potential approximation. The effective then obtained second step by mapping total energies associated rotations moments onto an classical...
We demonstrate that the magnetic properties of diluted semiconductors are dominated by short ranged interatomic exchange interactions have a strong directional dependence. By combining first principles calculations with classical Heisenberg model and Monte Carlo simulations, we reproduce observed critical temperatures broad range semiconductors. also show agreement between theory experiment is obtained only when atoms randomly positioned. This suggests ordering heavily influenced...
The local softness and the Fukui function emerge from density functional theory as measures of electronic reactivity. We obtain here an exact linear integral relation between functions insulators or molecules probability frontier orbitals Kohn–Sham theory. same map holds states at Fermi level for metals. kernel in those relations is inverse transpose potential response (PRF) PRF has form static Hartree dielectric with exchange correlation interaction added to bare Coulomb interaction. also...
We present a new method for the determination of electronic structure random transition-metal alloys, which combines simplicity empirical tight-binding schemes with accuracy first-principles treatments. Our uses linear muffin-tin orbitals description states and coherent-potential approximation to describe effect disorder. The central result our theory is expression configurationally averaged Green's-function matrix, then used evaluate various one-electron properties alloys. separation...
On the basis of ab initio calculations for Mn-doped GaN, GaP, GaAs and GaSb, we discuss origin ferromagnetism in diluted magnetic semiconductors. The use Korringa–Kohn–Rostoker method connection with coherent potential approximation to describe substitutional moment disorder. By mapping total energy results onto a Heisenberg model, Curie temperature TC is estimated mean field (MFA). If impurity bands are formed gap, as case (Ga, Mn)N, double exchange dominates leading characteristic...
Based on model and ab initio calculations we discuss the effect of resonant interface states conductance epitaxial tunnel junctions. In particular show that ``hot spots'' found by several groups in symmetrical barriers ${\mathbf{k}}_{\ensuremath{\Vert}}$-resolved can be explained formation bonding antibonding hybrids between both sides barrier. If resonance condition for these hybrid is met, electron tunnels through barrier without attenuation. Even when move together form a single...
Abstract This contribution reviews an ab initio two-step procedure to determine exchange interactions, spin-wave spectra, and thermodynamic properties of itinerant magnets. In the first step, self-consistent electronic structure a system is calculated for collinear spin at zero temperature. second parameters effective classical Heisenberg Hamiltonian are determined using magnetic force theorem one-electron Green functions. The methods statistical physics employed in subsequent evaluation...
We present ab initio calculations of magnetic moments and local electronic densities states in binary ${\mathrm{Fe}}_{3+\mathit{y}}$${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$ ternary ${\mathrm{Fe}}_{3\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{V}}_{\mathit{x}}$Si random alloys with ${\mathit{DO}}_{3}$-derived structures. The local-spin-density approximation, the linear muffin-tin orbital method, coherent-potential approximation (LMTO-CPA) were used. In excess (as compared to...
We present a first-principles study of the physical properties disordered ${\mathrm{Ni}}_{2\ensuremath{-}x}\mathrm{Mn}\mathrm{Sb}$ alloys which form continuous series connecting two typical members Heusler alloy family: namely, half-metallic semi-Heusler NiMnSb $(x=1)$ and related metallic ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{Sb}$ $(x=0)$. Magnetic moments, exchange interactions, magnon spectra, Curie temperatures at ambient elevated pressures are determined compared with available...
We perform a theoretical study of the magnetism induced in transition metal dioxides ZrO2 and TiO2 by substitution cation vacancy or an impurity from groups 1A 2A periodic table, where is either K Ca. In present both supercell embedded cluster methods are used. It demonstrated that K-impurity leads to robust magnetic moment on surrounding O-atoms for cubic rutile host crystals. On other hand it shown Ca-impurity non state. The native O-vacancy does not induce dioxide crystal.
Chemical reactivity theory provides a basis for predicting the reactive proclivities of molecular or condensed systems. The frontier-orbital concepts Fukui, as generalized by Parr and collaborators within framework density-functional theory, were developed further us in previous paper (I) [J. Chem. Phys. 101, 8988 (1994)]. Nevertheless, five aspects still require development; reactivities are defined local responses to global stimuli instead nonlocal stimuli; there ambiguities associated...
We study the effect of interface disorder on spin-dependent resistances Co/Cu, Fe/Cr, and Au/Ag multilayers using a newly developed method for calculating transmission matrices from first-principles. The efficient implementation tight-binding linear-muffin-tin orbitals allows us to model large lateral supercells whereby specular diffuse scattering are treated an equal footing. Without introducing any free parameters, quantitative agreement with experiment is obtained. predict that reduces...
The effective exchange interactions of magnetic overlayers Fe/Cu(001) and Co/Cu(001) covered by a Cu-cap layer varying thickness were calculated in real space from first principles. two-dimensional Heisenberg Hamiltonian was constructed used to estimate magnon dispersion laws, spin-wave stiffness constants, overlayer Curie temperatures within the mean-field random-phase approximations. Overlayer temperature oscillates as function cap-layer qualitative agreement with recent experiment.
We present a semi-analytic theory for the Curie temperature in diluted magnetic semi-conductors that treats disorder effects exactly effective Heisenberg Hamiltonian, and spin fluctuations within local RPA. The exchange couplings are taken from concentration dependent {\it ab initio} estimates. gives very good agreement with published data well-annealed samples of Mn$_x$Ga$_{1-x}$As. predict critical temperatures Mn$_x$Ga$_{1-x}$N lower than doped GaAs, despite stronger nearest-neighbour...
We use the local-density approximation (LDA) and $\mathrm{LDA}+U$ schemes to study magnetism of (GaMn)As (GaMn)N for a number Mn concentrations varying holes. show that both systems calculational presence holes is crucial establishing ferromagnetism. For systems, introduction U increases delocalization and, simultaneously, decreases $p\ensuremath{-}d$ interaction. Since these two trends exert opposite influences on Mn-Mn exchange interaction character variation Curie temperature ${T}_{C}$...
From the basis of ab initio electronic structure calculations which include effects thermally excited magnetic fluctuations, we predict Mn-stabilized cubic zirconia to be ferromagnetic above 500 K. We find this material, is well known both as an imitation diamond and a catalyst, half-metallic with majority minority spin Mn impurity states lying in zirconia's wide gap. The concentration can exceed 40%. high-${T}_{C}$ ferromagnetism robust oxygen vacancy defects how impurities are distributed...
The canonical method of Andersen and Jepsen for determining the band structure metals, which is based on linear muffin-tin orbital leads to an extremely simple tight-binding method, generalized case random alloys. factorization structural- potential-dependent parts allows one perform configurational averaging within single-site approximation. theory illustrated ${\mathrm{Ag}}_{\mathrm{x}}$${\mathrm{Pd}}_{100\mathrm{\ensuremath{-}}\mathrm{x}}$ alloy series.
We develop an efficient technique for ab initio calculations of the current-perpendicular-to-plane (CPP) electron transport in disordered magnetic multilayers. The method is based on tight-binding linear muffin-tin orbital theory and coherent potential approximation (CPA) to treat substitutional randomness effective-medium approach. A formulation CPA vertex corrections, giving rise incoherent part CPP conductance, described detail numerical implementation discussed. developed approach...
We propose to replace Ga in (Ga,Mn)As with Li and Zn as a route high Curie temperature, carrier mediated ferromagnetism dilute moment n-type semiconductor. Superior material characteristics, rendering Li(Zn,Mn)As realistic candidate for such system, include solubility of the isovalent substitutional Mn impurity concentration controlled independently doping by adjusting Li-(Zn,Mn) stoichiometry. Our predictions are anchored ab initio calculations comparisons familiar directly related...
We present results of systematic fully relativistic first-principles calculations the uniaxial magnetic anisotropy energy (MAE) a disordered and partially ordered tetragonal Fe-Co alloy using coherent potential approximation (CPA). This has recently become promising system for thin ferromagnetic films with perpendicular anisotropy. find that existing theoretical approaches to homogeneous random bulk alloys, based on simple virtual crystal (VCA), overestimate maximum MAE values obtained in...
We present an ab initio theory of transport quantities metallic ferromagnets developed in the framework fully relativistic tight-binding linear muffin-tin orbital method. The approach is based on Kubo-St\ifmmode \check{r}\else \v{r}\fi{}eda formula for conductivity tensor, coherent potential approximation random alloys, and concept interatomic electron transport. formalism applied to pure $3d$ transition metals (Fe, Co, Ni) Ni-based ferromagnetic alloys (Ni-Fe, Ni-Co, Ni-Mn). High values...