Specific heat and the dielectric properties of Bi$_{0.8}$Ho$_{0.2}$FeO$_{3}$ multiferroic

The specific heat and the dielectric permittivity of Bi$_{0.8}$Ho$_{0.2}$FeO$_{3}$ multiferroics have been studied in the wide temperature range 300–750 K. The doping with rare-earth element holmium is found to lead to substantial changes in the temperature dependences of specific heat $C_p$ and dielectric permittivity $\varepsilon'$ at high temperatures. The additional contribution to the specific heat is shown can be interpreted as a Schottky anomaly for three-level states which form due to a distortion of the lattice parameters as a result of doping. Additional anomaly characteristic of a phase transition is observed in temperature dependences of $C_p$ and $\varepsilon'$. The results are discussed in combination with the data of structural studies.