Piezomagnetism in uranium dioxide probed by x-ray diffraction in pulsed magnetic fields*

5f-electron spin systems exhibit strong spin-lattice coupling and electronic correlations and are predicted to host new emergent phenomena. One recent example is the observation of piezomagnetism and magneto-elastic memory effect in the antiferromagnetic Mott-Hubbard insulator, UO₂ [1]. Here, we give a short overview of piezomagnetic behavior in this material with a focus on X-ray diffraction studies of oriented UO₂ crystals under strong pulsed magnetic fields. We show how the high-resolution single-crystal diffraction allows us to study details of subtle unit-cell distortions below and above the structural and magnetic phase transition in this material. We show that direct microstructural observations of the piezomagnetic and switching effects are being a direct consequence of the non-collinear 3k magnetic order that breaks time-reversal symmetry in a non-trivial way. We also observe the presence of magnetic domains with distinct magnetic-field evolution in the magnetically ordered state of UO₂, both when the field is applied repeatedly in a single direction and when the field direction is alternated. 

[1] Jaime, M. et al. Piezomagnetism and magnetoelastic memory in uranium dioxide. Nat. Commun. 8, 99 (2017).