Frozen Superparaelectric State of Local Polar Regions in GdMn₂O₅ and Gd_0.8Ce_0.2MnO₅

A comparative study of the dielectric properties and electric polarization of multiferroics GdMn₂O₅ and Gd_0.8Ce_0.2MnO₅ has been carried out in the temperature range 5–330 K. The polarization properties in the ferroelectric state that forms due to a charge ordering and exchange striction have been studied at T ≤ T_C = 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 T_f ≫ T_C. Such a high-temperature polarization is due to the frozen superparaelectric state of the restricted polar domains.