Dynamics and performance optimization of spin-torque switching in magnetic tunnel junctions

Abstract

In this thesis I present a theoretical description for spin-torque switching using AC and DC spin-currents. This description builds from the standard Landau-Lifshitz-Gilbert equation with Slonczewski spin-torque. By exploiting a separation in time-scales between the fast precessional motion of the free layer magnetization about the effective field and the slow drift of the free layer towards higher or lower energies that results from ST and damping, I reduce the free layer switching dynamics to that of a one dimensional system. Using this description I characterize certain current and frequency values important to switching, such as the DC critical current and the AC upper bifurcation frequency. Finally, using this description I show how to optimize the efficiency of AC, DC, and combination AC/DC spin-current strategies to minimize the Joule heat loss associated with switching. This leads to a well-defined range of spin-current polarization and free layer anisotropy values where each spin-current strategy is optimal.