Magnetic Phase Transitions and Magnetic-Field-Induced Polarization Flops in Multiferroic YbMn2O5

Abstract

We have measured the electric polarization along the b - and a -axes of multiferroic YbMn 2 O 5 under a magnetic field along the c -axis up to 14.5 T. We found that the polarization along the b -axis disappears, while that along the a -axis appears below 5.5 K in 0 T, though the direction of the polarization switches again above 1.5 T at 4.3 K. Ferroelectric hysteresis loops along the both axes of YbMn 2 O 5 were clearly observed by the double-wave method. This polarization-flop phenomenon is very similar to that previously found in TmMn 2 O 5 . We have also studied the magnetic phase transitions of YbMn 2 O 5 by neutron diffraction, and compared the data with those of TmMn 2 O 5 . The low-temperature incommensurate magnetic phases relating to the polarization flop of YbMn 2 O 5 and TmMn 2 O 5 are similar, though YbMn 2 O 5 lacks a commensurate magnetic and ferroelectric phase which exists in TmMn 2 O 5 and typical similar compounds.