Antiferromagnetic Interfacial Coupling and Giant MagneticHysteresis in La0.5Ca0.5MnO3–SrRuO3 Superlattices

摘要

Superlattices are of great importance due to their potential as new materials genome to synthesize new functional materials. Thus, tuning of the ground state of superlattices is crucial to further control their physical properties. In this study, superlattices (SLs) consisting of alternating layers of SrRuO3 (SRO) (5 nm) and La0.5Ca0.5MnO3 (LCMO) (5 nm) are epitaxially grown on SrTiO3 (STO) and LaAlO3 (LAO) substrates with 10-unit-cell periods. A variation in the substrate-induced-strain for this choice of SLs triggers observation of remarkable properties, such as magnetic anisotropy and large magnetic hysteresis. The strain states experienced by LCMO and SRO in these SLs result in strong ferromagnetic interlayer coupling and weak antiferromagnetic interlayer coupling at low temperatures in SLs of LCMO–SRO/STO and a strong antiferromagnetic interlayer coupling in SLs of LCMO–SRO/LAO. Besides, a large magnetic hysteresis resulting from the predominant magnetic anisotropy of SRO together with the strength of magnetic coupling is observed in SLs of LCMO–SRO/LAO along the out-of-plane direction ofthe LAO substrate. These four different magnetic behaviors along fourdifferent directions of substrate orientations are interpreted interms of preferential orbital occupation and competing magnetic exchangecoupling together with magnetic anisotropy. This study demonstratesthe subtleties in controlling the strength of magnetic coupling atthe interface and stands as a model system to realize fascinatingmagnetic phenomena in layer-by-layer hetero-epitaxial oxide films.