Abstract: Entropy-stabilized materials are stabilized by the configurational entropy of the constituents, rather than the enthalpy of formation of the compound. These materials have attracted significant interest due to the apparent deviations from Gibbs phase rule and desirable mechanical properties. Despite the discovery of high entropy crystals nearly 15 years ago, reported investigations outside transition metal alloys have just recently been extended to ionic crystals, particularly oxides, a class of materials which can demonstrate useful and dynamic functional properties such as ferroelectricity, magnetoelectricity, thermoelectricity, and superconductivity. As the magnetic and electronic properties of oxides are strongly correlated to their chemistry and electronic structure, the concept of entropy stabilization could lead to interesting and novel properties. Though known entropy-stabilized oxides contain magnetic constituents, the magnetic properties of the multi-component oxide have yet to be investigated. Here we examine the role of entropy and composition on the exchange coupling and magnetic anisotropy of permalloy/(Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O thin film heterostructures. We observe a strong exchange field and an apparent deviation from the rule of mixtures in the structural and magnetic parameters. This result demonstrates that entropy stabilized oxides can be engineered to show concerted magnetic properties that are dependent on constituent species, yet differ from a simple weighed average of the components and can result in unexpected phenomena.
