Spin-Orbit Torque-Assisted Voltage-Controlled Magnetization Switching for Reliable Nonvolatile Memory

Abstract

Voltage-controlled magnetic or magnetoelectric random-access memory (VC-MRAM or MeRAM), which leverages the voltage-controlled magnetic anisotropy (VCMA) effect, enables efficient ultrafast device switching on subnanosecond time scales with write energy E w below femtojoules. However, the high write error rates (WER)-stemming from the oscillatory nature of voltage switching-hinders its development and necessitates precise time control of write pulses. Ideally, spin-orbit torque (SOT) can also support ultrafast magnetization switching, provided the current exceeds a critical threshold, determined by the magnetic anisotropy. Here, we demonstrate a back-end-of-line compatible device utilizing a Ta/Mo seed layer capable of operating in VC, SOT, or hybrid modes. In the hybrid mode, we apply subcritical SOT current to assist VCMA-induced switching. The WER of VC-MRAM can be reduced by over two orders of magnitude, which is attributed to modified magnetization dynamics and the change of micromagnetic free energy during the operation. The enhancement in WER results in an improved energy-delay product surpasses that of the conventional VC-MRAM scheme. Simulations further show that the improved performance positions the SOT-assisted VC-MRAM as a promising candidate for compute-in-memory applications, including binary neural networks.