Enhancing Interfacial Ferromagnetism and Magnetic Anisotropy of CaRuO₃/SrTiO₃ Superlattices via Substrate Orientation

Abstract

Artificial oxide heterostructures have provided promising platforms for the exploration of emergent quantum phases with extraordinary properties. One of the most interesting phenomena is the interfacial magnetism formed between two non‐magnetic compounds. Here, a robust ferromagnetic phase emerged at the (111)‐oriented heterointerface between paramagnetic CaRuO₃ and diamagnetic SrTiO₃ is reported. The Curie temperature is as high as ≈155 K and the saturation magnetization is as large as ≈1.3 µ_B per formula unit for the (111)‐CaRuO₃/SrTiO₃ superlattices, which are obviously superior to those of the (001)‐oriented counterparts and are comparable to the typical itinerant ferromagnet SrRuO₃. A strong in‐plane magnetic anisotropy with six‐fold symmetry is further revealed by the anisotropic magnetoresistance measurements, presenting a large in‐plane anisotropic field of 3.0–3.6 T. More importantly, the magnetic easy axis of the (111)‐oriented superlattices can be effectively tuned from 〈1〉 to 〈〉 directions by increasing the layer thickness of SrTiO₃. The findings demonstrate a feasible approach to enhance the interface coupling effect by varying the stacking orientation of oxide heterostructures. The tunable magnetic anisotropy also shows potential applications in low‐power‐consumption or exchange spring devices.