Calculation of the tunneling magnetoresistance (TMR) an epitaxial Fe/MgO/Fe(001) junction is reported. The conductances in its ferromagnetic and antiferromagnetic configurations are determined without any approximations from real-space Kubo formula using tight-binding bands fitted to ab initio band structure iron MgO. calculated optimistic TMR ratio excess 1000% for MgO barrier $\ensuremath{\approx}20$ atomic planes spin polarization current positive all thicknesses. It also found that...

The Gilbert damping constant present in the phenomenological Landau-Lifshitz-Gilbert equation describing dynamics of magnetization is calculated for ferromagnetic metallic films as well Co/nonmagnet (NM) bilayers. calculations are done within a realistic nine-orbital tight-binding model including spin-orbit coupling. convergence expressed sum over Brillouin zone remarkably improved by introducing finite temperature into electronic occupation factors and subsequent summation Matsubara...

We obtain closed-form analytic solutions for surface Green's functions within arbitrary multiorbital models. The formulation is completely general, and equally valid empirical tight binding, linear-muffin-tin-orbital screened Korringa-Kohn-Rostoker other Green's-function equivalent formalisms, where the Hamiltonian can be put into a localized (i.e., block-band) form. are applicable to finite or semi-infinite systems, with quite general substrate overlayers, even superlattices. This achieved...

A self-consistent theory of the current-induced switching magnetization using nonequilibrium Keldysh formalism is developed for a junction two ferromagnets separated by nonmagnetic spacer in ballistic limit. It shown that spin-transfer torques responsible can be calculated from first principles steady state when magnet stationary. achieved torque, proportional to bias voltage linear response regime, balanced torque due anisotropy fields. The expressed terms one-electron surface Green...

It is demonstrated by numerical evaluation of the real-space Kubo formula that tunneling magnetoresistance (TMR) due to between two cobalt electrodes separated a vacuum gap remains nonzero when one covered with copper layer. This contradicts classical theory predicts zero TMR. shown TMR quantum well states in Cu layer do not participate transport. Since these only occur down-spin channel, their loss from transport creates spin asymmetry electrons overlayer, i.e., mechanism could provide an...

We present calculational studies of the electronic and geometric structure an ordered monolayer deposition Bi on III-V(110) surfaces. The technique which we have applied to these systems relies complete self-consistent solution Kohn-Sham equations for both ionic degrees freedom. An ab initio pseudopotential method, within local-density approximation, is used in a supercell approach. From given initial set atomic positions, conjugate-gradient achieve equilibrium geometry by moving along...

Calculation of the tunneling magnetoresistance (TMR) an $\mathrm{Fe}∕\mathrm{Mg}\mathrm{O}∕\mathrm{Fe}(001)$ junction with a disordered $\mathrm{Fe}∕\mathrm{Mg}\mathrm{O}$ interface is reported. It shown that intermixing Fe and Mg atoms at decreases TMR ratio rapidly when about 16% interfacial are substituted by calculated saturates increasing MgO thickness in good agreement experiment. demonstrated saturation occurs because scattering leads to redistribution conductance channels, which...

Two parallel calculations of the exchange coupling in a Co/Cu/Co(001) trilayer, both using same realistic $s, p$, and $d$ tight-binding bands with parameters determined from ab initio band structures bulk Cu Co, are reported. The is first calculated within framework quantum-well (QW) formalism which periodic behavior spectral density exploited to derive an analytic formula for valid large spacer thicknesses. On other hand, alternative expression coupling, referred as cleavage formula,...

The results of a rigorous quantum calculation the current-perpendicular-to-plane giant magnetoresistance (CPP GMR) Co/Cu/Co(001) trilayer without impurity scattering are reported. conductances per spin in ferromagnetic (FM) and antiferromagnetic (AF) configurations magnetic layers computed from Kubo formula. electronic structure Cu Co is described by fully realistic s,p,d tight-binding bands fitted to ab initio band structures fcc Co. Depending on thickness, CPP GMR ratio can be as high 90%....

Abstract The interaction of P with 90° partial dislocations in Si is examined using a cluster method local-density-functional pseudopotential theory. This capable predicting structural properties such as bond lengths and angles to within few per cent. We describe several states at dislocation cores which are normally reconstructed contain solitonic bonding patterns. Our overall conclusion that there clear tendency for migrate towards the core, assume threefold coordination, thus firstly...

The Gilbert damping constant in the phenomenological Landau-Lifshitz-Gilbert equation which describes dynamics of magnetization, is calculated for Fe, Co and Ni bulk ferromagnets, films Co/Pd bilayers within a nine-band tight-binding model with spin-orbit coupling included. calculational effciency remarkably improved by introducing finite temperature into electronic occupation factors subsequent summation over Matsubara frequencies. dependence on scattering rate good agreement results...

The 90° partial dislocation is used as a model to study pinning by impurities in silicon. Several electrically active (As, B, N, P) are examined reinforcing earlier work on P and extending it, including realistic assessment of basis set effects. Strongest (3 eV per impurity atom) obtained association the with reconstruction defect (“soliton”), replacing threefold coordinated silicon site. Nitrogen was far most effective agent. In addition pairing energies found which generally slightly...

We make a theoretical study of the quantum oscillations tunneling magnetoresistance (TMR) as function spacer layer thickness. Such were recently observed in junctions with nonmagnetic metallic at barrier-electrode interface. calculate TMR ratio for disordered containing which well states are formed. A single-orbital tight-binding model, linear response theory, and coherent potential approximation used calculation. As thickness, calculated shows damped oscillation around zero single period...

Abstract The interaction of O with 90° partial dislocations in Si is examined using a cluster method local-density-functional pseudo-potential theory. We consider several states at dislocation cores firstly which are normally reconstructed and secondly contain solitonic bonding patterns. This topic has been the subject number experiments by Sumino his collaborators, our overall findings support conclusions.

A local-density-functional cluster method is used to calculate the structure and vibrational modes of interstitial oxygen in silicon. We find Si-O lengths Si-O-Si bond angle be 1.59 \AA{} 172\ifmmode^\circ\else\textdegree\fi{}, respectively. The asymmetric symmetric stretch frequencies are 1104 554 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ close observed at 1136 518 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. effective charge upper mode 3.5e. Isotopic shifts also reported. that independent...

The structure of dislocations in semiconductors and the effect their interaction with impurities are examined using an ab initio local density functional cluster method. This method is entirely free from any empirical parameters takes account charge transfer between impurity host as well forces acting on core atoms. It found that Si strongly reconstructed but B, P, N, As destroy this reconstruction. C have little effect. Oxygen atoms form clusters which aggregate near dislocation cores also...

Calculation of the magnetoresistance an epitaxial $\mathrm{Fe}∕\mathrm{Au}∕\mathrm{MgO}∕\mathrm{Au}∕\mathrm{Fe}(001)$ tunneling junction is reported. The (TMR) determined without any approximations from real-space Kubo formula using tight-binding bands fitted to ab initio band structure Fe, Au, and MgO. A very high TMR ratio $\ensuremath{\approx}1000%$ predicted for a with seven nine atomic planes MgO sandwiched between two Au layers, each consisting eight planes. insertion interlayers...

Calculations of the tunneling magnetoresistance (TMR) an epitaxial $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ junction attached to $n$-type GaAs lead, under positive gate voltage, are presented. It is shown that for realistic carrier densities TMR this composite system can be more than 2 orders magnitude higher a conventional junction. Furthermore, high achieved with modest MgO thicknesses and very robust disorder at $\mathrm{Fe}/\mathrm{GaAs}$ interface within layer itself. The significant...

We investigate theoretically spin-dependent transport through an epitaxial Fe/GaAs/Fe(001) tunnel junction with and without spin-orbit interaction. Calculations neglecting interaction the effect of $d$ orbitals on GaAs band structure predict that tunneling magnetoresistance (TMR) should increase increasing thickness barrier approach values close to perfect spin-valve limit. However, when and, in particular, is included TMR ratio saturates rapidly a rather modest value about 30% Fermi level...

A local density functional cluster method is used to investigate the structure of dislocations in Si and GaAs as well interaction P O impurities with Si. The 90° partial found be strongly reconstructed but are bound dislocation inhibit this reconstruction. also attracted core form stable di-interstitial oxygen complexes there. These results can account for strong pinning effects observed plastically deformed containing these impurities. In GaAs, Ga(g) (β) same way Si, As(g) (α) not. This may...

Calculation of the tunneling magnetoresistance (TMR) an Fe/Ag/MgO/Fe(001) magnetic junction is reported. The determined without any approximations from real-space Kubo formula using tight-binding bands fitted to ab initio band structure. It shown that calculated TMR oscillates as a function Ag interlayer thickness between positive values in excess 2000% and negative order $\ensuremath{-}100%$. oscillation period by spanning vector Fermi surface. large changes its sign are due resonant...

We theoretically study the dependence of tunnel magnetoresistance (TMR) an MgO-based magnetic junction (MTJ) on thickness ferromagnetic (FM) layers. Our results show that TMR ratio oscillates with FM The amplitude these oscillations is much greater than one expected to occur in giant devices. This explained by presence barrier, which reduces number propagating states, thus, limiting effect destructive interference and special nature ${\ensuremath{\Delta}}_{1}$ band Fe. Calculations taking...

The uniaxial in-plane magnetic anisotropy (UIP-MA) constant is calculated for a single step on the (001) surface of fcc $\mathrm{Co}(N)$ films. calculations are done both an undecorated and decorated with one or more, up to seven, Cu wires. Our objective explain mechanisms by which decoration decreases UIP-MA constant, effect observed experimentally ultrathin Co films deposited vicinal surfaces can lead reorientation magnetization within film plane. Theoretical performed realistic...

It is shown, within the quantum-well theory of exchange coupling $J$ in magnetic multilayers, that temperature dependence governed not only by spacer Fermi surface but also confining strength ferromagnetic layers. The confinement mechanism first explored for an exactly solvable parabolic-band model and cases which it leads to a very strong are identified. Finally, demonstrated, using fully realistic tight-binding bands, dominates $J(T)$ Co/Cu/Co(001).