Energy-efficient picosecond spin-orbit torque magnetization switching in ferro- and ferrimagnetic films

TL;DR

This study investigates ultrafast, energy-efficient magnetization switching in ferromagnetic and ferrimagnetic films using picosecond spin-orbit torques, revealing reduced energy costs and new reversal mechanisms at femtosecond timescales.

Contribution

It introduces a method to generate and analyze picosecond current pulses for SOT switching, demonstrating significant energy savings and a transition in reversal mechanisms at ultrafast durations.

Findings

Energy cost decreases by over an order of magnitude at picosecond pulses

Projected energy consumption of 9 fJ for 100x100 nm ferrimagnetic device

Transition from non-coherent to coherent magnetization reversal at ultrafast timescales

Abstract

Electrical current pulses can be used to manipulate magnetization efficiently via spin-orbit torques (SOTs). Pulse durations as short as a few picoseconds have been used to switch the magnetization of ferromagnetic films, reaching the THz regime. However, little is known about the reversal mechanisms and energy requirements in the ultrafast switching regime. In this work, we quantify the energy cost for magnetization reversal over 7 orders of magnitude in pulse duration, in both ferromagnetic and ferrimagnetic samples, bridging quasi-static spintronics and femtomagnetism. To this end, we develop a method to stretch picosecond pulses generated by a photoconductive switch by an order of magnitude. Thereby, we can create current pulses from picoseconds to durations approaching pulse width available with commercial instruments. We show that the energy cost for SOT switching decreases by more than an order of magnitude in all samples when the pulse duration enters the picosecond range. We project an energy cost of 9 fJ for a 100 x 100 nm 2 ferrimagnetic device. Micromagnetic and macrospin simulations unveil a transition from a non-coherent to a coherent magnetization reversal with a strong modification of the magnetization dynamical trajectories as pulse duration is reduced. Our results cement the potential for high-speed magnetic spin-orbit torque memories and highlights alternative magnetization reversal pathways at fast time scales.