Local structure of multiferroic TbMn2O5: Evidence for an anomalous Tb-O distribution

Abstract

The temperature dependent local structure of TbMn2O5 was determined by x-ray-absorption spectroscopy. An anomalous Tb-O distribution is found. At high temperature, it is broad but resolves into two distinct peaks below similar to 180 K. The distributions sharpen below the Tb magnetic ordering temperature (similar to 10 K). The distortions in the Tb-O distribution, away from the Pbam structure, are consistent with rotations of the MnOx polyhedra about the c axis and suggest that Tb-O bond polarization may play a significant role in the observed ferroelectric properties of this system.