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

TLDR

We investigate magnetization switching induced by spin‑Hall‑assisted spin‑transfer torque in a three‑terminal device comprising a perpendicular‑anisotropy magnetic tunnel junction and a β‑W strip. We simulate the free‑layer dynamics using a modified Landau–Lifshitz–Gilbert equation, evaluate the effects of spin‑Hall write‑current density, duration, and direction, and develop a Verilog‑A electrical model for transient simulation of a 4‑T/1‑MTJ/1‑β‑W memory cell. The switching time is reduced to less than 1 ns with a spin‑Hall current density of about 25 MA cm⁻² and a 0.5 ns pulse, and simulations show that spin‑Hall‑assisted STT‑MTJ outperforms conventional STT‑MTJ in both write speed and energy.

Abstract

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.