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Current-induced spin transfer torque in relatively thick Néel domain walls in ferromagnetic metals/semiconductors is considered theoretically in the linear response regime. Using quasiclassical approximation and unitary transformation we calculate the nonequilibrium (current-induced) spin accumulation in the domain wall. The current-induced spin density is then used to determine adiabatic and nonadiabatic components of the spin transfer torque. The results show that the spin torque as well as its nonadiabaticity can be enhanced by spin-conserving momentum scattering processes inside the wall. [ABSTRACT FROM AUTHOR]

Electrons interacting with a domain wall in ferromagnetic metals are considered theoretically. In the framework of semiclassical approximation and taking into account Coulomb interaction between electrons, we calculate the spin and charge distribution near the domain wall as well as the local conductivity. We show that the conductivity is significantly modified near the wall and also depends on electron–electron interaction.

We present a general approach to the problem of a ferromagnetic phase transition in diluted magnetic semiconductors with free carriers. The Curie temperature of ferromagnetic transition is calculated in the mean field approximation. The approach allows to analyze the effects of magnetic fluctuations and disorder on the Curie temperature. We also propose a new mechanism of exchange interaction between magnetic impurities at vanishing concentration of free carriers.

The influence of interband interactions on the location of impurity stages in narrow-gap and gapless semiconductors of AIVBVI type is considered in the T-matrix approximation. It is shown that taking account of the interband interaction results in diminution of the activation energy of the impurity level.

Mixed-valent states of rare-earth dopants in narrow-gap IV-VI semiconductors are analyzed. A theoretical approach to describing rare-earth-doped IV-VI semiconductors is proposed in which the dopant is considered a strongly correlated system, with electronic states coupled to conduction- and valence-band states. The results are illustrated by the example of the Yb dopant, having an almost-filledfshell. It is shown that the system can be described by a narrow resonance level, whose position and width depend on the chemical potential and band gap. The possibility of the formation of mixed-valent states is demonstrated.

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