Rémi Arras

Ru-deficient SrRuO ₃ films and BiFeO ₃ /SrRuO ₃ heterostructures show tunable low-field magnetocaloric effects via vacancies and interface coupling. Ru vacancies induce dual FM transitions and higher entropy, while BiFeO ₃ causes inverse MCE near T _N .

Two-dimensional (2D) van der Waals magnets offer a promising platform for pushing skyrmion technology to the single-layer limit with high tunability. While the Dzyaloshinskii-Moriya interaction (DMI) is often recognized as central to skyrmion formation, its stability, collapse, and topological transition in 2D materials remain largely unexplored. In particular, the effect of higher-order exchange interactions (HOI) on these phenomena is unknown. Here, using first-principles calculations and atomistic spin simulations, we report a new topological transition generated by HOI, which we term "ferric transition", in single-layer MnSeTe. Surprisingly, skyrmion stability and collapse remain largely unaffected by HOI due to the dominant role of the DMI near the saddle point, whereas the Bloch point is strongly modified, giving rise to this novel transition. Moreover, we predict that Janus MnSeTe exhibits remarkably high skyrmion energy barriers due to its strong DMI, among the highest reported for intrinsic 2D magnets.