Absence of induced ferromagnetism in epitaxial uranium dioxide thin films

Recently, Y. Sharma et al. [Adv. Sci. 9, 2203473 (2022)] claimed that thin films (~20 nm) of UO₂ deposited on perovskite substrates exhibit strongly enhanced paramagnetism (called ``induced ferromagnetism'' by the authors). Moments of up to 30.28em0exB/U atom were claimed in magnetic fields of 6 T. We have reproduced such films and, after characterization, have examined them with x-ray circular magnetic dichroism (XMCD) at the uranium M edges, a technique that is element specific. We do not confirm the published results. We find a small increase, as compared to the bulk, in the magnetic susceptibility of UO₂ in such films, but the magnetization versus field curves, measured by XMCD, are linear with field and there is no indication of any ferromagnetism. The absence of any anomaly around 30 K (the antiferromagnetic ordering temperature of bulk UO₂) in the XMCD signal suggests the films do not order magnetically.