Structural and optical properties of Mn–Co–Ni–O and Mn–Zn–Ni–O medium-entropy oxide films

Mn_1.56Co_0.96Ni_0.48O₄ and Mn₂Zn_0.2Ni_0.8O₄ medium-entropy thermal-sensitive films were prepared by a sputtering system. The effects of different annealing temperatures on the microstructure, surface morphology, and optical properties of the films were studied. We obtained films with a cubic spinel structure and dense film surface, and determined their refractive index and extinction coefficient values in the spectral range of 245–1000 nm. Finally, we measured the absorption spectra of both films in the mid- and far-infrared regions.