Light-induced reorientation transition in an antiferromagnetic semiconductor

TL;DR

This study demonstrates a photoinduced, metastable reorientation of the magnetic order in an antiferromagnetic semiconductor, achieved through ultrafast excitation, revealing a new method for controlling antiferromagnetic states for spintronic applications.

Contribution

It introduces a novel ultrafast, non-thermal method to induce and observe metastable magnetic reorientation in an antiferromagnetic semiconductor, highlighting potential for advanced spintronic devices.

Findings

Metastable reorientation occurs within 10 ps after photoexcitation.

The metastable state persists for over 150 ps before decaying.

Reorientation is driven by non-thermal, ultrafast excitation, not thermodynamic processes.

Abstract

Due to the lack of a net magnetic moment, antiferromagnets possess a unique robustness to external magnetic fields and are thus predicted to play an important role in future magnetic technologies. However, this robustness also makes them quite difficult to control, and the development of novel methods to manipulate these systems with external stimuli is a fundamental goal of antiferromagnetic spintronics. In this work, we report evidence for a metastable reorientation of the order parameter in an antiferromagnetic semiconductor triggered by an ultrafast quench of the equilibrium order via photoexcitation above the band gap. The metastable state forms less than 10 ps after the excitation pulse, and persists for longer than 150 ps before decaying to the ground state via thermal fluctuations. Importantly, this transition cannot be induced thermodynamically, and requires the system to be driven out of equilibrium. Broadly speaking, this phenomenology is ultimately the result of large magnetoelastic coupling in combination with a relatively low symmetry of the magnetic ground state. Since neither of these properties are particularly uncommon in magnetic materials, the observations presented here imply a generic path toward novel device technology enabled by ultrafast dynamics in antiferromagnets.