Phonon scattering by paramagnetic ions of europium and samarium in bismuth ferrite

Temperature dependences of the thermal diffusivity and thermal conductivity in multiferroic materials BiFeO$_{3}$, Bi$_{0.90}$Sm$_{0.10}$FeO$_{3}$, and Bi$_{0.90}$Еu$_{0.10}$FeO$_{3}$ were studied. Substitution of rare-earth ions of europium and samarium for bismuth ions in bismuth ferrite was found to decrease the phonon thermal conductivity in a wide temperature range. The decrease in the heat conductivity of bismuth ferrite was determined to result from resonance phonon scattering by paramagnetic ions of europium and samarium.