Bazaliy Y. Magnetic dynamics and spintronics in metallic, semiconductor, and superconductor nanostructures

The thesis provides a theoretical description of the spintronics devices. It details the new methods, developed by the author, and compares the results of the calculations with the experimental data. In the area of spin-transfer physics the cases of layered systems and magnetic domain walls are considered. In the layered systems case, several methods that provide switching diagrams were developed and successfully tested. It was found for the first time that a magnetic configuration corresponding to the energy maximum can be stabilized by a spin-transfer torque. The phenomenon of stabilization by repulsion was discovered. In the area of systems with continuous magnetization change, a leading (parallel, or adiabatic) term in the expression for the spin torque was obtained for the first time. Using this result, it was found that the spectrum of spin waves is modified in the presence of electric current flowing through a ferromagnet. Subsequently, the motion of a variety of magnetic domain walls in ferromagnetic nanostrips was analyzed. The vortex domain walls were studied using the method of collective coordinates, developed in the thesis. The method gave results in good agreement with the experimental data. In the area of semiconductor systems with spin-orbit interaction, a collective excitation known as the spin-galvanic mode was studied. The influence of the electrostatic Coulomb interaction on this mode was calculated and it was found that the spectrum undergoes quantitative changes, but does not become gapped. Suggestions for the experimental observation of the mode were made and possible outcomes of such experiments were modeled. In the area of superconductive spintronic devices, the critical temperature of the superconductor layer sandwiched between the two ferromagnetic layers was calculated. It was found that the critical temperature depends on the magnetic configuration of the ferromagnet-superconductor-ferromagnet structure. Using numerical methods developed in the thesis it was shown that experimental results can be explained by the asymmetry of the structure.