Room-Temperature Ferromagnetism with Strong Spin–Orbit Coupling Achieved in CaRuO₃ Interfacial Phase via Magnetic Proximity Effect

Abstract

Recently, theoretical and experimental research predicted that ferromagnets with strong spin−orbit coupling (SOC) could serve as spin sources with dramatically enhanced spin−orbit torque (SOT) efficiency due to the combination of spin Hall effect and anomalous Hall effect (AHE), presenting potential advantages over conventional nonmagnetic heavy metals. However, materials with a strong SOC and room-temperature ferromagnetism are rare. Here, we report on a ferromagnetic (FM) interfacial phase with Curie temperature exceeding 300 K in the heavy transition-metal oxide CaRuO 3 , in proximity to La 0.67 Sr 0.33 MnO 3 . Electron energy loss and polarized neutron reflectometry spectra reveal the strong charge transfer from Ru to Mn at the interface, triggering antiferromagnetic exchange interactions between interfacial Ru/Mn ions and thus transferring magnetic order from La 0.67 Sr 0.33 MnO 3 to CaRuO 3 . An obvious advantage of such interfacial phase is the enhanced anomalous Hall effect at temperatures from 150 to 300 K. Compared to the most promising room-temperature ferromagnetic oxide La 0.67 Sr 0.33 MnO 3 , the anomalous Hall conductivity σ xy AHE (or anomalous Hall angle θ H ) of CaRuO 3 / La 0.67 Sr 0.33 MnO 3 superlattices is increased by 30 (or 31) times at 150 K and 10 (or 3) times at 300 K. This work demonstrates a special approach for inducing ferromagnetism in heavy transition-metal oxides with strong SOC, offering promising prospects for all-oxide-based spintronic applications.