Electronic transition above room temperature in CaMn_7O_(12) films

摘要

We report on the electronic phase transition in CaMn_7O_(12) quadruple perovskite films synthesized by oxide molecular beam epitaxy on SrLaAlO_4 and La_(0.3)Sr_(0.7)Al_(0.65)Ta_(0.35)O_3 substrates. We use x-ray diffraction and transmission electron microscopy to confirm that the CaMn_7O_(12) phase has been realized. Temperature dependent resistivity measurements reveal a signature of a charge ordering phase transition at ≈425 K, consistent with bulk CaMn_7O_(12). 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.