Frozen Superparaelectric State of Local Polar Regions in GdMn2O5 and Gd0.8Ce0.2Mn2O5

A comparative study of the dielectric properties and electric polarization of multiferroics GdMn2O5 and Gd0.8Ce0.2Mn2O5 has been carried out in the temperature range from 5 up to 300 K. The polarization properties in the ferroelectric state that forms due to a charge ordering and exchange striction have been studied at T less than 30 K. The properties of the restricted polar phase separation domains formed in the crystals containing ions Mn3+ and Mn4+ have been studied, too. These domains exhibit the electric polarization in the temperature range from 5 K to some temperatures Tf lager than TC. Such a high-temperature polarization is due to the frozen superparaelectric state of the restricted polar domains.