Effect of isovalent cation substitution on the thermal, caloric, and magnetocaloric properties of the (La$_{1-y}$Eu$_{y}$)$_{0.7}$Pb$_{0.3}$MnO$_{3}$ manganites

Crystalline samples of the (La$_{1-y}$Eu$_{y}$)$_{0.7}$Pb$_{0.3}$MnO$_{3}$ ($y$ = 0, 0.2, 0.4, 0.5, 0.6, and 0.8) manganite solid solutions have been grown. Temperature dependences of the specific heat, thermal expansion, and high-intensity magnetocaloric effect have been investigated. A comparative analysis of the effect of isovalent cationic substitution on the thermal and caloric parameters of the ferromagnetic phase transition has been made. It has been shown that the growth of the Eu atom concentration leads to a decrease in the phase transition entropy and an increase in the baric coefficient $dT/dp$. Field and temperature dependences of the magnetocaloric effect have been established. It is demonstrated that, varying the ratio of cations, one can obtain the solid solutions with the maximum magnetocaloric effect value in fields of up to 6 kOe in a temperature range of 90–340 K. Owing to the similar reduced relative cooling powers, the investigated solid solutions can be used as reference solid-state cooling media in designing the cascade cooling systems.