Electronic transition above room temperature in CaMn7O12 films

Abstract

We report on the electronic phase transition in CaMn7O12 quadruple perovskite films synthesized by oxide molecular beam epitaxy on SrLaAlO4 and La0.3Sr0.7Al0.65Ta0.35O3 substrates. We use x-ray diffraction and transmission electron microscopy to confirm that the CaMn7O12 phase has been realized. Temperature dependent resistivity measurements reveal a signature of a charge ordering phase transition at ≈425 K, consistent with bulk CaMn7O12. The transition temperature is found to be relatively invariant to changes in the cation stoichiometry. Density functional theory calculations reveal the changes in atomic and electronic structure induced by the charge ordering transition.