Heat capacity and magnetocaloric effect in manganites La$_{0.7}$Sr$_x$Ba$_{0.3-x}$MnO$_3$

Results of an experimental study of the heat capacity ($C_p$), as well as direct and indirect measurements of the MCE ($\Delta T$, $\Delta S$) of La$_{0.7}$Sr$_{0.3-x}$Ba$_x$MnO$_3$ samples (${x = 0,\, 0.02,\, 0.05,\, 0.10}$) in the temperature range $80$–$400$ K and in magnetic fields up to $1.8$ T are presented. It is shown that the partial substitution of barium (Ba) for strontium (Sr) shifts $T_C$ and insignificantly decreases the magnetocaloric effect. The maximum value of the change in entropy in a field of $1.8$ T is $\Delta S = 1.6$ J/kg$\cdot$K for $x= 0.02$. The entropy change associated with the disordering of the magnetic system during the ferromagnetic-paramagnetic phase transition is estimated.