Ferroelectricity driven by charge ordering in the A-site ordered perovskite manganite SmBaMn2O6.

Phase transitions in charge and orbital degrees of freedom occur successively in the A-site ordered perovskite manganite SmBaMn2O6 at TCO1≈370K and TCO2≈190K. To determine the 3d electronic state in each phase, we performed crystal structure analyses on a single-crystal sample at 150, 300, and 400 K using synchrotron x-ray diffraction. The results indicate that the charge and orbital ordering on the distorted and alternately tilted MnO6 octahedra should accompany electric polarization in each MnO2 layer. The stacking of the polarized MnO2 layers along the c axis changes from a staggered configuration to a ferroic configuration at TCO2. [ABSTRACT FROM AUTHOR]