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 µB 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.

Charge-Transfer-Induced Interfacial Ferromagnetism in Ferromagnet-Free Oxide Heterostructures

“…For example, effective tuning of a magnetic easy axis for an interfacial FM phase was achieved in the CRO/SrTiO 3 superlattice (SL) just by varying the thickness of sublayers, showing potential applications in low-power-consumption or exchange spring devices. 21 In this paper, we pay attention to a special superlattice (SL) formed by two typical PM oxides: the 4d ruthenate CRO and 3d nickelate LNO. CRO is an orthorhombically structured PM metal, showing non-Fermi-liquid behavior at low temperatures.…”

“…If the interfacial FM phase can be generated in the heterostructures consisting of two nonmagnetic constituents, the magnetic moment would become more tunable. For example, effective tuning of a magnetic easy axis for an interfacial FM phase was achieved in the CRO/SrTiO 3 superlattice (SL) just by varying the thickness of sublayers, showing potential applications in low-power-consumption or exchange spring devices …”