Shear Strain Control of Multiferroic Magnetic Ordering for Giant Ferromagnetism

Abstract

The magnetic ordering of perovskite ferroelectric oxides is essential for enhancing their stability and minimizing energy losses in magnetoelectric devices. However, inducing a transition from a magnetically disordered state to an ordered one remains a formidable challenge. Here, we propose a chemical sulfurization method that significantly bolsters the magnetic ordering of multiferroic super-tetragonal phase BiFeO₃ thin film, thereby enhancing the magnetic properties. The sulfured films exhibit a robust magnetic transition temperature of 586 K. The remanent magnetization increases approximately 1.6 times in the out-of-plane direction and an impressive 62 times in the in-plane direction. Additionally, the magnetic easy axis transitions from the out-of-plane to the in-plane direction. The X-ray absorption spectroscopy and atomic scale investigation reveal a reconfiguration of the local electronic hybridization states in the film. The sulfur-induced shear strain is identified as the catalyst for a shift in the Fe–O hybridization, from the pyramid-like geometry of FeO₅ to the octahedral arrangement of FeO₆. This transformation is deemed the root cause of the observed magnetic transition in the films. This sulfur-induced strategy for electronic hybridization reconfiguration is expected to break new ground, offering innovative methodologies for modulating perovskite oxides, two-dimensional ferroelectric films, and other ferromagnetic functional thin films.