Stabilizing extraordinary disorder in single crystal high entropy oxides*

In functional oxides, compositional changes to the cation sublattice(s) enables tunability to electronic and/or magnetic phases. For correlated systems, even low levels of cation substitution can have a dominating influence on behavior due to the near degeneracy of the spin/charge/orbital energy scales. Further, the local distortion fields near doping sites often act as the catalysis for phase transitions. Controlling the type, number, and magnitude of these local distortions is highly desirable but often not experimentally accessible. We demonstrate the creation of exceptionally high disorder fields in single crystal oxides. Examples of epitaxial perovskite, spinel, and layered Ruddlesden-Popper phases possessing 5 or more elements randomly distributed on one or more of their cation sublattices. Synthesis of these materials relies on precise control of configuration entropy to dominate the free energy landscape, thus avoiding phase separation generally inherent in complex multinary systems. The impact of changing spin, charge, and lattice distortion field uniformity in these high entropy oxides will be discussed.