Abstract
With the development in fabrication techniques, magnetization dynamics in nanostructures is a key issue to characterize the performance of magnetic nanodevices. By employing the time dependent Green’s function theory, magnetization dynamics has been studied in several magnetic systems.
Starting from a basic Hamiltonian with spin-localized spin interaction, a Landau-Lifshitz-Gilbert (LLG) equation describing magnetization dynamics has been derived. Two kinds of systems have been considered specifically: quantum dot with normal leads, and quantum dot with ferromagnetic leads. Expressions of intrinsic Gilbert damping tensor as well as fluctuating torque are derived in terms of Green’s function. Our expression of Gilbert damping tensor resembles the one derived from scattering matrix theory in the limit of low temperatures and wide band approximation, but is suitable for general case.
Recently spin torque effect due to the presence of Rashba spin-orbit coupling (RSOC) opens the possibility of a new mechanism to manipulate magnetization. In this work, magnetization dynamics is investigated in a finite 2DEG system where current is driven by bias instead of electric field. In a tight binding model, numerical calculation shows similar magnetic field assist switching effect as in the experiment. Our formalism is feasible for the first principle calculation of magnetization dynamics.