Robust Ferrimagnetism and Switchable Magnetic Anisotropy in High‐Entropy Ferrite Film

Abstract Ferrimagnetic insulator materials are the enabling technology for the development of next‐generation magnetic devices with low power consumption, high operation speed, and high miniaturization capability. To achieve a high‐density memory device, a combined realization of robust saturation magnetization ( M s ), controllable magnetic anisotropy, and high resistivity (ρ) are highly demanded. Despite significant efforts that have been made recently, simultaneously achieving significant enhancements in these properties in a soft magnetic insulator material still remains a great challenge, severely limiting their practical application. Herein, a high‐entropy strategy in an ultra‐thin spinel ferrite (CrMnFeCoNi) 3 O 4 film is reported that exhibits concurrently a superior saturation magnetization ( M S = 1198 emu cm −3 ), low coercivity ( H C = 90 Oe), and excellent resistivity (ρ = 1233 Ω cm), as well as switchable magnetic anisotropy. The comprehensive lattice probing and microstructure analysis studies reveal that such desirable ferromagnetic properties originate from the high‐quality structurally ordered but compositionally disordered single‐crystal epitaxial structure. The switchable magnetic anisotropy demonstrated in the high‐entropy ferrite film can be attributed to the new antiferromagnetic rock‐salt phase. This work unveils the critical benefits of the high‐entropy strategy for magnetic oxide thin films, which opens up new opportunities for the development of high‐performance magnetic materials.