We show in this paper recent results on the spin resistivity in magnetically ordered materials obtained by Monte Carlo simulations. We discuss its behavior as a function of temperature in various types of crystal: ferromagnetic, antiferromagnetic, and frustrated spin systems. In the model used for simulations, we take into account the interaction between itinerant spins and that between lattice spins and itinerant spins. We also include a chemical potential term, as well as an electric field. We study in particular the behavior of the spin resistivity at and near the magnetic phase transition where the effect of the magnetic ordering is strongest. In ferromagnetic crystals, the spin resistivity shows a sharp peak very similar to the magnetic susceptibility. This can be understood if one relates the spin resistivity to the spin-spin correlation as suggested in a number of theories. The dependence of the shape of the peak on physical parameters such as carrier concentration, magnetic field strength, relaxation time etc. is discussed. In antiferromagnets, the peak is not so pronounced and in some cases it is absent. Its direct relationship to the spin-spin correlation is not obvious. As for frustrated spin systems with strong first-order transition, the spin resistivity shows a discontinuity at the phase transition. To show the efficiency of the simulation method, we compare our results with recent experimental data performed on semiconducting MnTe of NiAs structure. We observe a very good agreement with experiments on the spin resistivity in the whole range of temperature.
We investigate several issues related to the electronic states in the ligand orbital of a given transition-metal salt as, for example, a K₂CuCl₄·2H₂O-type compound. In fact, to get our calculation, we start from an expression for the electronic density of states in a compound of the above type. In addition, various aspects related to superexchange interaction in both the paramagnetic and ferromagnetic cases are discussed and the electronic conduction process in the ligand orbital is studied.
Reflection of electrons from a potential barrier in heterostructures is described. An electric field of the barrier causes spin splitting of electron energies via the spin-orbit interaction and its form is calculated in the three-level k·p model for a nontrivial case of unbound electrons. It is shown that if the potential barrier is the only source of the spin-orbit interaction, the spin-flip electron reflections are not possible. However, there appear two unexpected possibilities related to the spin-orbit interaction: (a) non-attenuated electron propagation in the barrier whose height exceeds the energies of incoming electrons, (b) total reflection of electrons whose energies exceed barrier's height. It is indicated that the system can serve as a source of spin-polarized electron beams.
Investigation of electrical resistivity ρ and magnetoresistance in single crystalline n-type silicon heavily doped with antimony in the temperature range ΔT=5-300 K and at the magnetic inductance B up to 8 T was performed. It was established that, for the temperature range ΔT=25-300 K the conductivity is of activation type, while for ΔT=5-25 K it is of variable range hopping and is described by the Mott law. Parameters of the Mott hopping were calculated. It was shown that, to explain the experimental data, the spin polarized hopping via the occupied states has to be taken into account. The obtained parameters revealed that for the low temperature range ΔT=5-11 K the spin polarized hopping dominates, while for ΔT=11-20 K the spin polarized transport is accompanied by the wave function contraction.
The paper presents experimental study of the spin Seebeck effect based on the widely used ferromagnetic Co₇₉Si₁₀X layer, partially covered with Pt layer. The total thickness of tested sample is about 20 μm, which makes it the first confirmed presence of the spin Seebeck effect in bulk material. Experiment was carried out under magnetic flux density 300 mT, room temperature and for constant temperature difference across the sample ranging from 1 K to 21 K. The measured value of induced voltage drop achieved 0.5 μV per 1 K.
Spin wave modes in antiferromagnetically exchange-coupled magnetic double layers are analyzed theoretically. The considered structure is assumed to be covered by a nonmagnetic metallic layer. The spin wave frequencies and spin wave life times are determined from the macroscopic description based on the Landau-Lifshitz-Gilbert equation, which includes the torque due to spin pumping to the cap layer.
An overview of the achieved Inverse Spin Hall Effect voltage (V_{ISHE}) is presented to find upper limit of this V_{ISHE}. Comprehensive review confirms that the most significant spin systems are based on YIG substrate. The Pt ISHE interfaces are the most popular, however, the best result was reported for the Ir₂₀Mn₈₀ ISHE interface. Moreover, in this paper the transvers spin Seebeck effect (SSE) is measured in bulk sample of Ni_{76.1}Fe_{15.9}Cu_{4.3}Mo_{3.6} with Pt interface. The max. measured value of V_{ISHE} for NiFeCuMo alloy with Pt is 0.493 μV with ΔT= 21.5 K.
Taking into account the available experimental results, we model the electronic properties and current-voltage characteristics of a ferromagnet-semiconductor junction. The Fe/GaAs interface is considered as a Fe/(i-GaAs)/n⁺-GaAs/n-GaAs multilayer structure with the Schottky barrier. We also calculate numerically the current-voltage characteristics of a double-Schottky-barrier structure Fe/GaAs/Fe, which are in agreement with available experimental data. For this structure, we have estimated the spin current in the GaAs layer, which characterizes spin injection from the ferromagnet to the semiconductor.
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