Significantly Enhanced Room-Temperature Ferromagnetism in Multiferroic EuFeO 3-δ Thin Films.

Regulating the magnetic properties of multiferroics lays the foundation for their prospective application in spintronic devices. Single-phase multiferroics, such as rare-earth ferrites, are promising candidates; however, they typically exhibit weak magnetism at room temperature (RT). Here, we significantly boosted the RT ferromagnetism of a representative ferrite, EuFeO 3 , by oxygen defect engineering. Polarized neutron reflectometry and magnetometry measurements reveal that saturation magnetization reaches 0.04 μ B /Fe, which is approximately 5 times higher than its bulk phase. Combining the annular bright-field images with theoretical assessment, we unravel the underlying mechanism for magnetic enhancement, in which the decrease in Fe-O-Fe bond angles caused by oxygen vacancies ( V O ) strengthens magnetic interactions and tilts Fe spins. Furthermore, the internal relationship between magnetism and V O was established by illustrating how the magnetic structure and magnitude change with V O configuration and concentration. Our strategy for regulating magnetic properties can be applied to numerous functional oxide materials.