Thermal and magnetocaloric properties of manganites La$_{0.7}$Sr$_{0.3-x}$Ba$_{x}$MnO$_{3}$

The results of a study of the effect of partial substitution of Sr$^{2+}$ ions by Ba$^{2+}$ ions on the thermophysical and magnetocaloric properties of manganite La$_{0.7}$Sr$_{0.3-x}$Ba$_{x}$MnO$_{3}$ ($x$ = 0; 0.02; 0.05 and 0.10) in the temperature range 100–400 K and in a magnetic field up to 1.8 T. It is shown that such a substitution leads to a significant decrease in $T_C$. In the behaviour of the thermal diffusivity $\eta(T)$ and thermal conductivity $\kappa(T)$ near $T_C$, minima were found that are associated with both the scattering of phonons by local distortions of the crystal lattice and by spin fluctuations. The absolute values of thermal conductivity decrease with an increase in the disorder parameter. The magnetocaloric effect exhibits a weak dependence on the substitution level $(x)$.