Thermophysical properties of multiferroics Bi$_{1-x}$Tm$_x$FeO$_3$

Investigations of the heat capacity, thermal diffusivity, and thermal conductivity of multiferroics Bi$_{1-x}$Tm$_x$FeO$_3$ ($x$ = 0, 0.05, 0.10, 0.20) have been carried out in the high temperature range of 300–1200 K. and thermal conductivity in the region of phase transitions. The temperature dependences of the specific heat for compositions with $x$ = 0.10 and 0.20 exhibit an additional anomaly characteristic of the phase transition at $T$ = 580 K. The dominant mechanisms of phonon heat transfer in the region of ferroelectric and antiferromagnetic phase transitions are considered. The temperature dependence of the average phonon mean free path is determined.