Abstract: Generally, uniformity in materials is seen as critical to phase order, with disorder and defects being thought to result in lower ordering temperatures and prevention of long-range percolation. However, disorder is an important aspect of many materials systems – from alloys to dilute magnetic semiconductors. It can be used to manipulate superconductivity, magnetic ordering, and design degeneracies. High entropy materials are an evolution of this understanding and work in this field has begun to demonstrate that disorder is a parameter which can drive local microstates into globally ordered behaviors.

In this symposium, theoretical and experimental results exploring the role of disorder in manipulating spin, charge, lattice and electronic order parameters in two classes of single crystal high entropy oxide epitaxial films are discussed. First, in exploring magnetism, electronic structure and valence of the high entropy ABO₃ perovskite La_1-xSr_x(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃. Second, in an experimental realization of extreme A-site cation disorder in (Y_0.2La_0.2Nd_0.2Sm_0.2Gd_0.2)NiO₃, whose parent ternary oxides each have a large range of electronic (metal to insulator transition) and structural phase transition temperatures. These results suggest cation size, spin, and charge variance, such as that accessible only in high entropy oxides, can be critical in the design of next generation electronic, structural, and magnetic materials.