High-temperature structural evolution of hexagonal multiferroic YMnO₃and YbMnO₃

Neutron powder diffraction studies on the structural evolution of hexagonal multiferroic YMnO 3 and YbMnO 3 from 1000 K to 1400 K, and from 1000 K to 1350 K, respectively, are presented. The temperature evolution of diffraction patterns suggests that YMnO 3 undergoes a phase transition to a non-polar structure above 1200 K, while YbMnO 3 remains ferroelectric up to 1350 K. Detailed structural parameters were obtained as a function of temperature from Rietveld refinements. Based on this result, the distinct differences in temperature behaviour between YMnO 3 and YbMnO 3 , and the origin of the ferroelectricity in these hexagonal multiferroics are discussed.