Pulse Shaping Strategies for Efficient Switching of Magnetic Tunnel Junctions by Spin-Orbit Torque

TL;DR

This paper demonstrates that tailored pulse shaping significantly reduces the energy required for switching magnetic tunnel junctions via spin-orbit torque, without sacrificing speed or reliability, through experimental and simulation studies.

Contribution

It introduces optimized pulse shapes for SOT-induced MTJ switching, achieving up to 50% energy reduction compared to traditional square pulses.

Findings

Shaped pulses reduce switching energy by up to 50%.

Pulse shape impacts switching time and temperature rise.

Optimal pulse includes preheating, maximum amplitude, and lower amplitude phases.

Abstract

The writing energy for reversing the magnetization of the free layer in a magnetic tunnel junction (MTJ) is a key figure of merit for comparing the performances of magnetic random access memories with competing technologies. Magnetization switching of MTJs induced by spin torques typically relies on square voltage pulses. Here, we focus on the switching of perpendicular MTJs driven by spin-orbit torque (SOT), for which the magnetization reversal process consists of sequential domain nucleation and domain wall propagation. By performing a systematic study of the switching efficiency and speed as a function of pulse shape, we show that shaped pulses achieve up to 50% reduction of writing energy compared to square pulses without compromising the switching probability and speed. Time-resolved measurements of the tunneling magnetoresistance reveal how the switching times are strongly impacted by the pulse shape and temperature rise during the pulse. The optimal pulse shape consists of a preheating phase, a maximum amplitude to induce domain nucleation, and a lower amplitude phase to complete the reversal. Our experimental results, corroborated by micromagnetic simulations, provide diverse options to reduce the energy footprint of SOT devices in magnetic memory applications.