Multi‐Method Characterization of the High‐Entropy Spinel Oxide Mn 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Fe 2 O 4 : Entropy Evidence, Microstructure, and Magnetic Properties

Abstract The novel spinel Cu 0.2 Co 0.2 Mn 0.2 Ni 0.2 Zn 0.2 Fe 2 O 4 comprising six transition metal cations was successfully prepared by a solution‐combustion method followed by distinct thermal treatments. The entropic stabilization of this hexa‐metallic material is demonstrated using in situ high temperature powder X‐ray diffraction (PXRD) and directed removal of some of the constituting elements. Thorough evaluation of the PXRD data yields sizes of coherently scattering domains in the nanometre‐range. Transmission electron microscopy based methods support this finding and indicate a homogeneous distribution of the elements in the samples. The combination of 57 Fe Mössbauer spectroscopy with X‐ray absorption near edge spectroscopy allowed determination of the cation occupancy on the tetrahedral and octahedral sites in the cubic spinel structure. Magnetic studies show long‐range magnetic exchange interactions which are of ferri‐ or ferromagnetic nature with an exceptionally high saturation magnetization in the range of 92–108 emu g −1 at low temperature, but also an anomaly in the hysteresis of a sample calcined at 500 °C.