Perpendicular-anisotropy magnetic tunnel junction switched by spin-Hall-assisted spin-transfer torque

We investigate the magnetization switching induced by spin-Hall-assisted spin-transfer torque (STT) in a three-terminal device consisting of a perpendicular-anisotropy magnetic tunnel junction (MTJ) and an β-W strip. Magnetization dynamics in free layer of MTJ is simulated by solving numerically a modified Landau–Lifshitz–Gilbert equation. The influences of spin-Hall write current (density, duration and direction) on the STT switching are evaluated. We find that the switching speed of a STT-MTJ can be significantly improved (reduced to <1 ns) by using a sufficiently large spin-Hall write current density (∼25 MA cm⁻²) with an appropriate duration (∼0.5 ns). Finally we develop an electrical model of three-terminal MTJ/β-W device with Verilog-A language and perform transient simulation of switching a 4 T/1MTJ/1β-W memory cell with Spectre simulator. Simulation results demonstrate that spin-Hall-assisted STT-MTJ has advantages over conventional STT-MTJ in write speed and energy. (paper)