24 research outputs found
Evidence for a Magnetic Proximity Effect up to Room Temperature at Fe/(Ga,Mn)As Interfaces
No full textWe report x-ray magnetic circular dichroism and superconducting quantum interference device magnetometry experiments to study magnetic order and coupling in thin Fe/(Ga,Mn)As(100) films. We observe induced magnetic order in the (Ga,Mn)As layer that extends over more than 2 nm, even at room temperature. We find spectroscopic evidences of a hybridized d configuration of Mn atoms in Fe/(Ga,Mn)As, with negligible Mn diffusion and/or MnFe intermixing. We show by experiment as well as by theory that the magnetic moment of the Mn ions couples antiparallel to the moment of the Fe overlayer
S. Bulak-Balakhovich and jewish pogoms in the Belarusian Polesya territory
No full textThe article is devoted to the study of the actions of armed groups under the command of S. Bulak-Balakhovich regarding the Jewish population in the territory of Belarusian Polesie in 1920, their antisemitic character is shown.Статья посвящена изучению действий вооруженных формирований под командованием С. Булак-Балаховича в отношении еврейского населения на территории белорусского Полесья в 1920 г., показан их антисемитский характер
Spin-wave stiffness and micromagnetic exchange interactions expressed by means of the KKR Green function approach
No full textWe represent an approach to calculate micromagnetic model parameters such as the tensor of exchange stiffness, Dzyaloshinskii-Moriya interaction (DMI), as well as spin-wave stiffness. The scheme is based on the fully relativistic Korringa-Kohn-Rostoker Green function (KKR-GF) technique and can be seen as a relativistic extension of the work of Lichtenstein et al. [J. Magn. Magn. Mater. 67, 65 (1987)]. The expression for Dzα elements of DMI differ from the expressions for Dxα and Dyα elements as the former are derived via second-order perturbation term of the energy caused by spin-spiral while the latter are associated with the first-order term. Corresponding numerical results are compared with those obtained using other schemes reported in the literature
Composition-dependent magnetic response properties of Mn1−xFexGe alloys
No full textThe composition-dependent behavior of the Dzyaloshinskii–Moriya interaction (DMI), the spin-orbit torque (SOT), as well as anomalous and spin Hall conductivities of Mn1−xFexGe alloys have been investigated by first-principles calculations using the relativistic multiple scattering Korringa–Kohn–Rostoker (KKR) formalism. The Dxx component of the DMI exhibits a strong dependence on the Fe concentration, changing sign at x≈0.85 in line with previous theoretical calculations as well as with experimental results demonstrating the change of spin helicity at x≈0.8. A corresponding behavior with a sign change at x≈0.5 is predicted also for the Fermi-sea contribution to the SOT, because this is closely related to the DMI. In the case of anomalous and spin Hall effects it is shown that the calculated Fermi-sea contributions are rather small and the composition-dependent behavior of these effects are determined mainly by the electronic states at the Fermi level. The spin-orbit-induced scattering mechanisms responsible for both these effects suggest a common origin of the minimum of the anomalous Hall effect and the sign change of the spin Hall effect conductivities
Chemical bond formation showing a transition from physisorption to chemisorption
No full textSurface molecules can transition from physisorption through weak van der Waals forces to a strongly bound chemisorption state by overcoming an energy barrier. We show that a carbon monoxide (CO) molecule adsorbed to the tip of an atomic force microscope enables a controlled observation of bond formation, including its potential transition from physisorption to chemisorption. During imaging of copper (Cu) and iron (Fe) adatoms on a Cu(111) surface, the CO was not chemically inert but transited through a physisorbed local energy minimum into a chemisorbed global minimum, and an energy barrier was seen for the Fe adatom. Density functional theory reveals that the transition occurs through a hybridization of the electronic states of the CO molecule mainly with s-, p(z)-, and d(z)(2)-type states of the Fe and Cu adatoms, leading to chemical bonding
Composition-dependent magnetic response properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Fe</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi>Ge</mml:mi></mml:mrow></mml:math> alloys
No full textMagnetic properties of free
No full textAn ab initio theoretical investigation on the finite-temperature
magnetism of free metallic clusters is presented. The exchange
coupling between local magnetic moments in Fe clusters of 9–89 atoms
was calculated within the multiple-scattering formalism. From the
results an effective classical Heisenberg Hamiltonian was constructed,
and the magnetization as a function of temperature was obtained via
Monte Carlo simulations. It is found that the effective critical
temperature is
not a monotonous function of the cluster size. We demonstrate that for
a proper description of finite-temperature magnetism of free clusters,
the site dependence of the exchange coupling must be taken into
account
Finite-temperature magnetism of Fex Pd1-x and Cox Pt1-x alloys
No full textThe finite-temperature magnetic properties of FexPd1-x and CoxPt1-x alloys have been investigated. It is shown that the temperature-dependent magnetic behavior of these alloys cannot be described properly unless the coupling between the magnetic moments at the Fe and Co mediated through the interactions with the induced magnetic moments of the nonmagnetic Pd and Pt atoms is included. A scheme for the calculation of the Curie temperature (T-C) for this type of systems is presented that is based on the extended Heisenberg Hamiltonian with the appropriate exchange parameters J(ij) obtained from ab initio electronic-structure calculations. Within the present study the Korringa-Kohn-Rostoker Green's-function method has been used to calculate the Jij parameters. The Curie temperatures obtained for Fe(x)Pd(1-)x and CoxPt1-x alloys are compared with the corresponding experimental data. The experimental results for FexPd1-x alloys have been obtained within anomalous Hall-effect measurements. The agreement between theoretical results and all available experimental data is rather good
Effects of spin-orbit coupling on the spin structure of deposited transition-metal clusters
No full textThe influence of the spin-orbit coupling on the magnetic structure of deposited transition-metal nanostructures has been studied by fully relativistic electronic-structure calculations. The interplay of exchange coupling and magnetic anisotropy was monitored by studying the corresponding magnetic torque calculated within ab initio and model approaches. We find that a spin-orbit-induced Dzyaloshinski-Moriya interaction has a profound effect on the spin structure of such complex magnetic systems and that in combination with magnetic anisotropies and isotropic exchange this can result in peculiar magnetic properties
Anion substitution effects on structure and magnetism of the chromium chalcogenide Cr<sub>5</sub>Te<sub>8</sub> Part III: Structures and magnetism of the high-temperature modification Cr<sub>1+x</sub>Q<sub>2</sub> and the low-temperature modification Cr<sub>5+x</sub>Q<sub>8</sub> (Q = Te, Se; Te:Se = 5:3)
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