Manipulating Synergetic Effect of Atomic-Level Chemical and Structural Fluctuations on Magnetism in High-Entropy Oxides

High-entropy oxides, which incorporate five or more distinct cations into a single crystallographic site, are attracting significant attention, owing to their often unexpected physical and chemical properties. However, understanding and manipulation of local chemical compositions and structures and their dominance on material performance remain a significant challenge. Here, we investigate a prototype antiferromagnetic high-entropy oxide (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O with rocksalt-type structure, and directly visualize local fluctuating lattice distortions and short-range ordering using advanced scanning transmission electron microscopy imaging. Degrees of chemical homogeneity and lattice distortions can be synergistically manipulated through thermal treatment temperatures, leading to correlative changes in the antiferromagnetic interaction and magnetic properties. We propose that local chemical and structural fluctuations synergistically affect magnetic interactions, with higher-temperature sintering reducing fluctuations and enhancing magnetic coupling. This work provides insights into the tunability of local fluctuating compositions and structures in high-entropy oxides, contributing to the desired functionalities in more high-entropy materials.