Ultrashort spin-orbit torque generated by femtosecond laser pulses

TL;DR

This paper demonstrates the generation of ultrashort spin-orbit torque pulses using femtosecond laser pulses to control magnetization precession at an epitaxial Fe/GaAs interface, advancing ultrafast spintronics.

Contribution

It introduces a method to produce and control ultrashort SOT pulses via femtosecond laser excitation, enabling scalable high-speed magnetic switching.

Findings

Ultrashort SOT pulses excite Larmor precession at Fe/GaAs interface.

Laser pulses are converted into high-amplitude current pulses in a photodiode.

The polarity, amplitude, and direction of current pulses are controllable.

Abstract

To realize the very objective of spintronics, namely the development of ultra-high frequency and energy-efficient electronic devices, an ultrafast and scalable approach to switch magnetic bits is required. Magnetization switching with spin currents generated by the spin-orbit interaction at ferromagnetic/non-magnetic interfaces is one of such scalable approaches, where the ultimate switching speed is limited by the Larmor precession frequency. Understanding the magnetization precession dynamics induced by spin-orbit torques (SOTs) is therefore of great importance. Here we demonstrate generation of ultrashort SOT pulses that excite Larmor precession at an epitaxial Fe/GaAs interface by converting femtosecond laser pulses into high-amplitude current pulses in an electrically biased p-i-n photodiode. We control the polarity, amplitude, and duration of the current pulses and, most importantly, also their propagation direction with respect to the crystal orientation. The SOT origin of the excited Larmor precession was revealed by a detailed analysis of the precession phase and amplitude at different experimental conditions.