Thermal physical and dielectric properties of Bi$_{1-x}$Er$_{x}$FeO$_{3}$

The heat capacity and the permittivity of multiferroics Bi$_{1-x}$Er$_{x}$FeO$_{3}$ ($x$ = 0, 0.10, and 0.15) have been studied in the temperature range 130–800 K. It is found that an insignificant substitution of erbium for bismuth significantly increases the heat capacity in a wide temperature range $T>$ 300 K. The temperature dependence of the excess heat capacity is shown to be due to manifestation of the three-level states. An additional anomaly characteristic of a phase transition has been revealed in the temperature dependences of the heat capacity and the permittivity for the compositions with $x$ = 0.15 at $T$ = 587 K. The results of studies are discussed in combination of the data of structural studies.