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ABSTRACT: Anomalous and spin Hall effects are investigated theoretically for a magnetic
tunnel junction where the applied voltage produces a Rashba spin-or bit
coupling within the tunneling barrier layer. The ferromagnetic electrodes are
the source of the spin-polarized current. The tunneling electrons experience a
spin-orbit coupling inside the barrier due to the applied electrical field.
Charge and spin Hall currents are calculated as functions of the position
inside the barrier and the angle between the magnetizations of the electrodes.
We find that both charge and spin Hall currents are located inside the barrier
near the in terfaces. The dependence of the currents on magnetic configuration
of the magnetic tunnel junction makes possible the manipulation by the Hall
currents via rotation of the magnetization of the electrodes.
05/2013;
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ABSTRACT: Coherent potential approximation (CPA) has widely been used for studying
residual resistivity of bulk alloys and electrical conductivity in
inhomogeneous systems with structural disorder. Here we revisit the single-site
CPA within the Landauer-B\"uttiker approach applied to the electronic transport
in layered structures and show that this method can be interpreted in terms of
the B\"uttiker's voltage-probe model that has been developed for treating phase
breaking scattering in mesoscopic systems. We demonstrate that the on-site
vertex function which appears within the single-site CPA formalism plays a role
of the local chemical potential within the voltage-probe approach. This
interpretation allows the determination of the chemical potential profile
across a disordered conductor which is useful for analyzing results of
transport calculations within the CPA. We illustrate this method by providing
several examples. In particular, for layered systems with translational
periodicity in the plane of the layers we introduce the local resistivity and
calculate the interface resistance between disordered layers.
02/2012;
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ABSTRACT: We consider the magnetic phase diagram of the two-dimensional Hubbard model
on a square lattice. We take into account both spiral and collinear
incommensurate magnetic states. The possibility of phase separation of spiral
magnetic phases is taken into consideration as well. Our study shows that all
the listed phases appear to be the ground state at certain parameters of the
model. Relation of the obtained results to real materials, e.g. Cu-based
high-temperature superconductors, is discussed.
09/2011;
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ABSTRACT: A new magnetoelectric effect is predicted originating from the interlayer exchange coupling between two ferromagnetic layers separated by an ultrathin ferroelectric barrier. It is demonstrated that ferroelectric polarization switching driven by an external electric field leads to a sizable change in the interlayer exchange coupling. The effect occurs in asymmetric ferromagnet/ferroelectric/ferromagnet junctions due to a change in the electrostatic potential profile across the junction affecting the interlayer coupling. The predicted phenomenon indicates the possibility of switching the magnetic configuration by reversing the polarization of the ferroelectric barrier layer.
Journal of Physics Condensed Matter 09/2010; 22(35):352203. · 2.55 Impact Factor
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ABSTRACT: We present a quantum statistical treatment of the Giant Magnetoresistance (GMR) in multilayers with an arbitrary number of
layers and arbitrary angles between the magnetization vectors in the magnetic layers. The intrinsic potential and the exchange
splitting of the conducting electron band is taken into account. The developed approach was successfully applied to the description
of the GMR in combination multilayers.
01/2008: pages 43-57;
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ABSTRACT: Localized impurity or defect states in the insulating barrier layer separating two ferromagnetic films affect dramatically the interlayer exchange coupling (IEC), making it significantly stronger compared to perfect barriers. We demonstrate that the impurity-assisted IEC becomes antiferromagnetic if the energy of the impurity states matches the Fermi energy and that the coupling strength decreases with temperature. These results explain available experimental data on the IEC across tunnel barriers.
Physical Review Letters 02/2005; 94(2):026806. · 7.37 Impact Factor
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ABSTRACT: We calculate the resistivity and Giant Magnetoresistance (GMR) of a segmented nanowire consisting of two ferromagnetic segments separated by a thin paramagnetic spacer. The quantization of the electron motion due to the small nanowire cross-section is taken into account; s-d electron scattering gives rise to different mean free paths for spin-up and spin-down s-electrons. The calculated resistivity and GMR oscillate as a function of nanowire cross-section due to the difference in Fermi momenta of d-electrons with opposite spins. The GMR can reach values much higher than those which are obtained for "wires" of infinite cross-section (i.e., a multilayer). Similarly we have calculated the Tunneling Magnetoresistance (TMR) by replacing the paramagnetic spacer with an insulator spacer.
03/2000;
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ABSTRACT: We calculate the resistivity and giant magnetoresistance (GMR) of a segmented nanowire consisting of two ferromagnetic segments separated by a thin paramagnetic spacer. Spin-dependent surface electron scattering is taken into account. The quantization of the electron motion due to the small nanowire cross section leads to oscillations of the resistivity and the GMR. The interplay between spin-dependent electron scattering in the bulk and the surface results in a complex behavior of the GMR as a function of nanowire radius and surface-potential strength. Both increase and decrease of the GMR can be obtained as the spin-dependent surface scattering grows.
Phys. Rev. B. 63(17).
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ABSTRACT: We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and decreases exponentially with MgO thickness. Oxygen vacancies placed in the middle of MgO make IEC antiferromagnetic for three monolayers (MLs) of MgO, but do not change the sign of IEC for five MLs. The latter fact is explained within the model, which suggests that for the impurity level lying below the Fermi energy IEC can change sign with increasing barrier thickness due to the weaker coupling of the impurity level to the ferromagnets.
Journal of Magnetism and Magnetic Materials.
