Exchange-striction driven ultrafast nonthermal lattice dynamics in NiO

TL;DR

This study reveals ultrafast, nonthermal lattice dynamics in NiO driven by exchange striction, showing how spin-lattice coupling can be manipulated on femtosecond timescales for potential control of magnetic order.

Contribution

It demonstrates the use of femtosecond electron diffraction to observe nonthermal lattice states and transient exchange striction effects in NiO.

Findings

Identification of a nonthermal lattice state within 0.3 ps

Observation of preferential O ion displacement over Ni ions

Detection of transient Q-asymmetry of Friedel pairs

Abstract

We use femtosecond electron diffraction to study ultrafast lattice dynamics in the highly correlated antiferromagnetic (AF) semiconductor NiO. Using the scattering vector (Q) dependence of Bragg diffraction, we introduce a Q-resolved effective lattice temperature, and identify a nonthermal lattice state with preferential displacement of O compared to Ni ions, which occurs within ~0.3 ps and persists for 25 ps. We associate this with transient changes to the AF exchange striction-induced lattice distortion, supported by the observation of a transient Q-asymmetry of Friedel pairs. Our observation highlights the role of spin-lattice coupling in routes towards ultrafast control of spin order.