Room-temperature tuning of magnetic anisotropy in samarium-thulium orthoferrites

Rare-earth orthoferrites (RFeO₃) provide a flexible playground for magnetic materials design, combining the magnetic properties arising from complex interactions between R³⁺ and Fe³⁺ cations within the robust framework of the perovskite structure. The most important magnetic property common to most orthoferrites is a spin reorientation transition in which the magnetic moments of Fe³⁺ cations rotate with respect to a crystallographic axis. SmFeO₃ is unique among orthoferrites due to its high-temperature spin reorientation. It is possible to tune the spin reorientation transition to occur at room temperature by replacing Sm with Tm in the Sm0.70Tm0.30FeO₃ perovskite. In this study, we show how small changes in composition in the Sm_1-xTmₓFeO₃ (x=0.30--0.50) series provide a high degree of control over the magnetic properties. This work also offers a rather unusual look into the magnetic structure of a samarium-based perovskite by means of neutron powder diffraction, which was made possible by using ¹⁵²Sm. The combination of these results and magnetization measurements allowed the construction of the magnetic phase diagram of the series.