  High entropy oxides (HEO)s have garnered much interest due to their available
high degree of tunability. Here, we study the local structure of
(MgNiCuCoZn)0.167(MnCr)0.083O, a composition based on the parent HEO
(MgNiCuCoZn)0.2O.We synthesized a series of thin films via pulsed laser
deposition at incremental oxygen partial pressures. X-ray diffraction shows
lattice parameter to decrease with increased pO2 pressures until the onset of
phase separation. X-ray absorption fine structure shows that specific atomic
species in the composition dictate the global structure of the material as Cr,
Co, and Mn shift to energetically favorable coordination with increasing
pressure. Transmission electron microscopy analysis on a lower-pressure sample
exhibits a rock salt structure, but the higher-pressure sample reveals
reflections reminiscent of the spinel structure. In all, these findings give a
more complete picture on how (MgNiCuCoZn)0.167(MnCr)0.083O forms with varying
initial conditions and advances fundamental knowledge of cation behavior in
high entropy oxides.
