Ultrafast optically induced ferromagnetic state in an elemental antiferromagnet

TL;DR

This study demonstrates an ultrafast, optically induced transition to a ferromagnetic state in antiferromagnetic Mn within Co/Mn multilayers, occurring on a femtosecond timescale and driven by interface effects.

Contribution

It provides experimental evidence and theoretical explanation for a transient ferromagnetic state induced by optical pulses in an antiferromagnetic material.

Findings

Transient ferromagnetic signal observed at Mn L3 resonance.

The effect occurs within the duration of the pump pulse.

Theoretical calculations link the phenomenon to interface-induced population imbalance.

Abstract

We present evidence for an ultrafast optically induced ferromagnetic alignment of antiferromagnetic Mn in Co/Mn multilayers. We observe the transient ferromagnetic signal at the arrival of the pump pulse at the Mn L$_3$ resonance using x-ray magnetic circular dichroism in reflectivity. The timescale of the effect is comparable to the duration of the excitation and occurs before the magnetization in Co is quenched. Theoretical calculations point to the imbalanced population of Mn unoccupied states caused by the Co interface for the emergence of this transient ferromagnetic state.