Magnetoelastic standing waves induced in UO₂ by microsecond magnetic field pulses

We performed magnetoelastic measurements of the piezomagnetic antiferromagnet UO₂ via the Fiber Bragg Grating method in pulsed magnetic fields up to 150 T generated by a single-turn coil setup. While still insufficient to suppress the robust low temperature magnetically ordered state, we show that the uniquely short timescales of a few micro seconds of the magnetic-field pulse excite mechanical elastic resonances in the sample due to the piezomagnetic coupling. This results in standing-wave magnetoelastic oscillations superimposed on the magnetostriction signal. We compare the resonances with natural resonance frequencies obtained by a resonant ultrasound technique. The piezomagnetic switching behavior of the antiferromagnetic ordering vector below T_N=30.5K, which was revealed in a previous study [M. Jaime et al., Nature Communications 8, 99 (2017).] results in an apparent phase shift of π in the lattice oscillations. We further present a model to explain our data.