In this paper we explore the combined action of large thermal fluctuations and spin transfer torques on the behavior of magnetic layers in spin valves. We find that at temperatures near Tc, spin currents can measurably change the size of the magnetization (i.e. there is a longitudinal spin transfer effect), and we propose an experimental signature for this effect. We also find the temperature dependence of the applied-field applied-current phase diagram for a free magnetic layer, valid for temperatures near the Curie temperature Tc. In this study we employ both an atomistic stochastic Landau-Lifshitz-Slonczewski simulation at high temperatures, and also find the thermally averaged magnetic dynamics within mean field theory, yielding a Landau-Lifshitz- Bloch + Slonczewski equation. We show that this simplified equation describes the full stochastic model reasonably well. We also show how the Landau-Lifshitz-Gilbert equation describing a fixed magnetization size can be modified to describe the magnetic dynamics in this temperature regime.
Citation: Physical Review B
Pub Type: Journals
Spin transfer torque, magnetic dynamics, Curie temperature