Thermodynamic properties of Bi$_{0.8}$Dy$_x$Er$_{1-x}$FeO$_3$

The thermodynamic properties of the Bi$_{0.8}$Dy$_x$Er$_{1-x}$FeO$_3$ multiferroic have been studied in the temperature range of 120–800 K. It is shown that when bismuth ferrite is doped with two rare-earth elements erbium and dysprosium, a two-phase rhombohedral $R3c$ and orthorhombic $P_{nma}$ structure is realized and leads to an additional contribution to the heat capacity in a wide temperature range, a shift in the temperature of the antiferromagnetic phase transition to the low temperature region and an increase in magnetization with an increase in the concentration of dysprosium. Additional information found on temperature dependencies anomaly of heat capacity and dielectric constant for compositions with $x$ = 0.05 and 0.15 at $T\approx$ 542 and 577 K, respectively, indicate that it may be due to a structural phase transition between rhombohedral and orthorhombic structures.