Temperature behavior of the order parameter in Pb5Ge3O11

The temperature dependence of the spontaneous polarization in the Pb5Ge3O11 lead germanate (PGO) is experimentally investigated using optical, magneti c resonance, and conventional electrical measurements. The deviations from the temperature dependence typical of second-order phase transitions at tem peratures below 420 K are explained in terms of incomplete polarization swi tching and polarization induced by a residual depolarization field. The low -temperature anomalies are interpreted without consideration of additional structural transformations. The internal bias field is determined from the experimental temperature dependence of the perfect polarization of PGO sing le crystals in an electric field. (C) 2001 MAIK "Nauka/Interperiodica".