Heat capacity and dielectric properties of multiferroics Bi1-x Gd x FeO3 (x=0-0.20)

The heat capacity and the permittivity of multiferroics Bi1 - x Gd (x) FeO3 (x = 0, 0.05, 0.10, 0.15, 0.20) have been studied in the temperature range 130-800 K. It has been found that insignificant substitution of gadolinium for bismuth markedly shifts the temperature of antiferromagnetic phase transition and increases the heat capacity over a wide temperature range. It has been shown that the temperature dependence of the excess heat capacity is due to the manifestation of three-level states. Additional anomalies characteristic of the phase transitions have been revealed in the temperature dependences of the heat capacity for the compositions with x = 0.1 and 0.15 at T a parts per thousand 680 K and T a parts per thousand 430 K, respectively. The results of studies of the heat capacity have been discussed simultaneously with the data of structural studies.