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A domain wall (DW) which moves parallel to a magnetically compensated interface between an antiferromagnetic insulator (AFMI) and a two-dimensional (2D) metal can pump spin polarization into the metal. It is assumed that localized spins of a collinear AFMI interact with itinerant electrons through their exchange interaction on the interface. We employed the Keldysh formalism of Green's functions for electrons which experience potential and spin-orbit scattering on random impurities. This formalism allows a unified analysis of spin pumping, spin diffusion and spin relaxation effects on a 2D electron gas. It is shown that the pumping of a nonstaggered magnetization into the metal film takes place in the second order with respect to the interface exchange interaction. At sufficiently weak spin relaxation this pumping effect can be much stronger than the first-order effect of the Pauli magnetism which is produced by the small nonstaggered exchange field of the DW. It is shown that the pumped polarization is sensitive to the geometry of the electron's Fermi surface and increases when the wave vector of the staggered magnetization approaches the nesting vector of the Fermi surface. In a disordered diffusive electron gas the induced spin polarization follows the motion of the domain wall. It is distributed asymmetrically around the DW over a distance which can be much larger than the DW width. [ABSTRACT FROM AUTHOR]

The injection of a pure spin current into a conducting helimagnet is investigated. The characteristic decay lengths for the spin current injected into the helimagnet are determined, and their physical meaning is described. It is shown that instead of the spin diffusion length, helimagnets are characterized by the decay length that is always smaller than the spin diffusion length, the difference in these lengths being determined by the ratio of the helimagnet spiral period to the spin diffusion length. We predict the existence of the "effect of the chiral polarization of a pure spin current," i.e., the emergence of the spin current with longitudinal (transverse) polarization, which depends on the spiral chirality, upon the injection of a pure spin current with the transverse (longitudinal) polarization relative to the spiral axis. [ABSTRACT FROM AUTHOR]

We investigate features of electron emission from atoms in the field of the fundamental and second harmonic of a laser in conditions relevant to those realized in free-electron lasers. General expressions for the angular anisotropy and photoelectron spin polarization are obtained. These expressions are used for describing of the ionization of the valence shell of inert gas atoms and illustrated by calculations for neon. The possibility of control over the electron emission characteristics by varying the relative phase between harmonic (i.e., realization of one of the forms of the coherent control) is considered. [ABSTRACT FROM AUTHOR]

We have investigated the spin-induced voltage in the Hanle effect and the spin polarization factor of electrons in lateral spin devices based on InSb semiconductors with different electron concentrations. It is found that with increasing electron concentration, both the voltage and the polarization factor decrease. [ABSTRACT FROM AUTHOR]

The nonequilibrium magnetization (spin polarization) of conducting electrons moving in materials with a nonuniform magnetization distribution is analyzed theoretically. Both stationary states and transient processes occurring upon the current switching on and off are considered. Because of the coordinate dependence of the magnetization, the passage of current leads to a deviation of the charge carrier magnetization from its equilibrium value. Based on a simple model for nonequilibrium magnetization, the expression describing the coordinate dependence of the nonequilibrium magnetization is obtained in terms of the drift length and the spin diffusion length. It is shown that the effect is the strongest when the coordinate derivative of the magnetization is maximal. Various examples of media with a nonuniform magnetization are considered, including periodic structures such as spin density waves and artificial superlattices. [ABSTRACT FROM AUTHOR]

Possible second-order magnetic phase transitions to the incommensurate magnetic structure in the orthorhombic phase of LiMn2O4 compound have been investigated. It is shown that "weak Lifshitz condition" holds for this compound (i.e., Lifshits invariants are immaterial in all transitions being considered), and only the incommensurate phase, in which the wavevector near the transition point varies continuously with temperature and pressure, can be formed. A transition is considered both in the exchange approximation occurring in three irreducible representations forming an exchange multiplet as well as in one and two irreducible representations. Expressions have been derived for the mean density of the magnetic moment emerging because of such transitions. It is found that structures of the types of a longitudinal spin wave, a transverse spin wave with polarization along the crystallographic axes perpendicular to the wavevector of the structure, as well as certain superpositions of these waves can be formed in the system. [ABSTRACT FROM AUTHOR]

Abstract: The dynamics of the motion of the magnetic moment averaged over an ensemble of nonequilibrium spin-injected electrons in a ferromagnetic junction is considered with allowance for the exchange interaction, as well as the interaction with an external electromagnetic field and a thermostat. The solution of this problem is important for the experimental development of compact terahertz-band radiation sources. The rate of quantum transitions of electrons with opposite spins, which determine the spin relaxation under the interaction with a thermostat, is calculated within the density matrix formalism. It is shown that two spin-relaxation modes can be implemented that correspond to low- and high-Q precession of spin-nonequilibrium injected electrons. The effect of the characteristic features of spin-flip transitions under the relaxation of the magnetic moment on the emission and absorption of photons with-energy corresponding to the energy of effective exchange splitting of spin subbands is discussed. [ABSTRACT FROM AUTHOR]

The dynamics of Dirac-Weyl spin-polarized wavepackets driven by a periodic electric field is considered for the electrons in a mesoscopic quantum dot formed at the edge of the two-dimensional HgTe/CdTe topological insulator with Dirac-Weyl massless energy spectra, where the motion of carriers is less sensitive to disorder and impurity potentials. It is observed that the interplay of strongly coupled spin and charge degrees of freedom creates the regimes of irregular dynamics in both coordinate and spin channels. The border between the regular and irregular regimes determined by the strength and frequency of the driving field is found analytically within the quasiclassical approach by means of the Ince-Strutt diagram for the Mathieu equation, and is supported by full quantum-mechanical simulations of the driven dynamics. The investigation of quasienergy spectrum by Floquet approach reveals the presence of non-Poissonian level statistics, which indicates the possibility of chaotic quantum dynamics and corresponds to the areas of parameters for irregular regimes within the quasiclassical approach. We find that the influence of weak disorder leads to partial suppression of the dynamical chaos. Our findings are of interest both for progress in the fundamental field of quantum chaotic dynamics and for further experimental and technological applications of spindependent phenomena in nanostructures based on topological insulators. [ABSTRACT FROM AUTHOR]

The electronic structure and the optical properties of the HoCoSi and ErNiSi compounds are studied. Spin-polarized band calculations are performed in the local electron density approximation corrected for the strong electron-electron interactions in the 4 f shell of a rare-earth ion (LSDA + U method [11]). The optical constants are measured by ellipsometry in a wide wavelength range, and the frequency dependences of a number of spectral parameters are determined. The calculated densities of states are used to interpret the structural features of the interband optical conductivities of the intermetallic compounds. [ABSTRACT FROM AUTHOR]

The collision integral in the kinetic equation for a rarefied spin-polarized gas of fermions (electrons) is derived. The collisions between these fermions and the collisions with much heavier particles (ions) forming a randomly located stationary background (gas) are taken into account. An important new circumstance is that the particle-particle scattering amplitude is not assumed to be small, which could be obtained, for example, in the first Born approximation. The derived collision integral can be used in the kinetic equation, including that for a relatively cold rarefied spin-polarized plasma with a characteristic electron energy below α m c, where α is the fine-structure constant. [ABSTRACT FROM AUTHOR]

The ground-state energy of polarized and unpolarized liquid He is calculated using the variational theory. A variational wave function is constrained to be normalized appropriately by including the three-body terms in the cluster expansion of the two-body radial distribution function. The higher-order terms have been found to be important to obtain an equation of state which is in agreement with experimental data. The saturation density of unpolarized liquid He was found to be 0.267σ, which decreases by enhancing the polarization. For all relevant densities, the ground-state energy of the spin-polarized system is higher than that in the unpolarized case. [ABSTRACT FROM AUTHOR]