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The interference quantum correction to the conductivity and its temperature and magnetic-field dependence with taking into account the spin relaxation processes is investigated. The results of numerical and real physical experiments are reported. We show that the shape of the magnetoresistance is nonuniversal beyond the diffusion regime, when the close trajectories with small number of collisions are of importance. It is sensitive to anisotropy of scattering and correlation of impurity distribution.

We report on the spectroscopic magnetooptical studies of spin dynamics in diluted magnetic semiconductor (DMS) GaAs/AlGaAs/ZnSe/ZnCdMnSe heterovalent double quantum wells (QW). The transients of circularly polarized photoluminescence in an external magnetic field are detected in the structures with different widths of the GaAs QW. The analysis of the data, performed within the rate-equation model, has allowed separate estimations of the spin relaxation rate of localized electrons and holes. The spin flip of the electrons confined in the DMS ZnCdMnSe QW is faster than 20 ps, whereas the spin flip of the heavy hole localized in the GaAs QW is as long as ~9 ns. The long spin flip of the holes is presumably governed by their strong 3-dimensional localization.

We report on a considerable impact of light on spin transport in unstrained n-type GaAs. Increasing the intensity of optical spin pumping results in a significant expansion of spin diffusion. Furthermore, in the regime of strong spin pumping the spin gradient, which can be interpreted in terms of a spin outflow from the injection point is enhanced by application of a weak magnetic field. In addition we report on optical spin pumping of modulation doped CdTe-based quantum wells. Using a two-color Hanle-MOKE technique, we find a spin relaxation time of 34 ns in the nearly unperturbed electron gas. Independent variation of pump and probe energies demonstrates the presence of additional electrons in the quantum well, whose spin relaxation time is substantially shorter.

Photoluminescence measurements on individual CdSe/ZnSe/ZnMnSe quantum dots in a magnetic field up to 11 T both parallel and perpendicular to the sample growth plane at 1.6 K reveal a qualitative difference between samples with different strength of the sp-d exchange interaction controlled by means of varying the thickness of the nonmagnetic ZnSe layer. The observed difference is related with the dependence of the non-radiative Mn assisted recombination and the spin relaxation on magnetic field and the strength of the exchange interaction.

Exciton recombination in asymmetric CdMgTe/CdTe/CdMgTe/CdTe/CdMnTe double quantum wells (ADQW) with different barrier widths is studied in magnetic field up to 10 T. As grown structures were subjected to temperature annealing to introduce Mn and Mg atoms from the barriers into the CdTe quantum wells (QW). At low fields exciton transition in QW with magnetic impurity (Mn) is higher in energy than that in QW with nonmagnetic impurity (Mg), and interwell exciton relaxation is fast independently on the spin state. In contrast, at high fields, when the energy order reverses, an unexpectedly low relaxation rate of σ^- polarized excitons from nonmagnetic QW to the ground σ⁺ polarized state in magnetic QW has been observed. Effect strongly correlates with hh–lh splitting value Δ_hh–lh and discussed in terms of valence band mixing. Such a slowing down of relaxation allows separation of oppositely polarized excitons in different QWs.

The dependence of spin relaxation on the direction of the quantum wire under Rashba and Dresselhaus (linear and cubic) spin-orbit coupling is studied. Comprising the dimensional reduction of the wire in the diffusive regime, the lowest spin relaxation and dephasing rates for (001) and (110) systems are found.

Spin relaxation process is simulated for nanowires and 2-D channels composed of II–VI DMS materials, particularly for Cd_1-xMn_xTe, in our work. Our studies are focused on analyzing spin relaxation behavior at T = 1 K. Variations in spin relaxation length with applied field and concentration of Mn doping are calculated and plotted. Effect of one-magnon scattering process is significant due to magnetic nature of the materials and is demonstrated in this work.

Recent experimental reports suggest the formation of a highly spin-polarized interface ("spinterface") between a ferromagnetic (FM) Cobalt (Co) electrode and a metal-phthalocyanine (Pc) molecule. Another report shows an almost 60% giant magnetoresistance (GMR) response measured on Co/H₂Pc-based single molecule spin valves. In this paper, we compare the spin injection and transport properties of organic spin valves with two different organic spacers, namely Tris(8-hydroxyquinolinato) aluminum (Alq₃) and CoPc sandwiched between half-metallic La_0.7Sr_0.3MnO₃ (LSMO) and Co electrodes. Alq₃-based spin valves exhibit clear and reproducible spin valve switching with almost 35% negative GMR at 10 K, in accordance with previous reports. In contrast, cobalt-pthalocyanine (CoPc)-based spin valves fail to show clear GMR response above noise level despite high expectations based on recent reports. Investigations of electronic, magnetic and magnetotransport properties of electrode/spacer interfaces of LSMO/CoPc/Co devices offer three plausible explanations for the absence of GMR: (1) CoPc films are strongly chemisorbed on the LSMO surface. This improves the LSMO magnetic properties but also induces local traps at the LSMO interface for spin-polarized charge carriers. (2) At the Co/CoPc interface, diffusion of Co atoms into the organic semiconductor (OS) layer and chemical reactivity between Co and the OS deteriorates the FM properties of Co. This renders the Co/CoPc interface as unsuitable for efficient spin injection. (3) The presence of heavy Co atoms in CoPc leads to large spin–orbit coupling in the spacer. The spin relaxation time in the CoPc layer is therefore considerably smaller compared to Alq₃. Based on these findings, we suggest that the absence of GMR in CoPc-based spin valves is caused by a combined effect of inefficient spin injection from FM contacts and poor spin transport in the CoPc spacer layer.

Interplay between magnetization dynamics and electric current in a conducting ferromagnet is theoretically studied based on a microscopic model calculation. First, the effects of the current on magnetization dynamics (spin torques) are studied with special attention to the "dissipative" torques arising from spin-relaxation processes of conduction electrons. Next, an analysis is given of the "spin motive force", namely, a spin-dependent 'voltage' generation due to magnetization dynamics, which is the reaction to spin torques. Finally, an attempt is presented of a unified description of these effects.

The dependence of spin relaxation on the direction of the quantum wire under Rashba and Dresselhaus (linear and cubic) spin-orbit coupling is studied. Comprising the dimensional reduction of the wire in the diffusive regime, the lowest spin relaxation and dephasing rates for (001) and (110) systems are found.