Linking Local Structure to Functionality in High-Entropy Oxides*

High-entropy oxides (HEOs) represent a new frontier in functional ceramics, where extreme chemical disorder enables properties unattainable in conventional materials. By combining multiple cations on a single sublattice, HEOs harness configurational entropy to stabilize phases and expand the accessible design space. This talk narrates how structural and functional behavior in HEOs can be tuned by composition and processing. We show that disorder can be leveraged to control magnetic transitions, structural phases, and other emergent phenomena in both bulk and thin-film forms. Polycrystalline powders and epitaxial films are synthesized using solid-state and physical vapor-based methods, then characterized with magnetometry, X-ray diffraction, synchrotron spectroscopy, and electron microscopy to probe behavior across multiple length scales. These measurements reveal how subtle changes in local coordination and cation distribution drive large shifts in macroscopic properties. Importantly, we find that entropy-driven design strategies not only stabilize unusual phases but also allow systematic control over magnetic, structural, and electronic responses. This framework highlights new routes for tailoring performance in systems where conventional approaches are limited. By bridging atomic-scale disorder with application-relevant properties, these studies expand our understanding of disorder–property relationships and establish high-entropy ceramics as versatile platforms for sensing, magnetic, and energy technologies. The results underscore how chemical complexity, far from being a barrier, can be a deliberate tool for materials discovery.