Measurement of complicated temperature-dependent polarization of multiferroic RMn₂O₅

We have measured the temperature-dependent electric polarization P(T) of multiferroic rare-earth (R) manganese oxides RMn₂O₅ using both typical pyroelectric measurements and hysteresis loops with the double-wave method (DWM), and revealed the complicated behavior of the P(T). RMn ₂O₅ single crystal samples often exhibit a tendency to macroscopically polarize without applying an external electric field. We have found that the tendency appeared in P(T) by the pyroelectric measurement can be measured by the DWM loops. The tendency to polarize is equivalent to asymmetric non-hystersis loops obtained by the DWM. We clarify the relationship between P(T) by pyroelectric measurement and that by the DWM loops, which can warrant the measured P(T).