Effect of R substitution on magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 compounds with R=Ce, Pr and Nd

Magnetic properties and magnetocaloric effects of La$_{1 - x}R_{x}$Fe$_{11.5}$Si$_{1.5}$ ($R$=Pr, ($0 \le x \le 0.5$); $R$ = Ce and Nd, ($0 \le x \le 0.3$)) compounds are investigated. Partially replacing La with $R$ = Ce, Pr and Nd in La$_{1 - x}R_{x}$Fe$_{11.5}$Si$_{1.5}$ leads to a reduction in Curie temperature due to the lattice contraction. The substitution of $R$ for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change $\Delta S_{\rm m}$ and also in hysteresis loss. However, a high effective refrigerant capacity $RC_{\rm eff}$ is still maintained in La$_{1 - x}R_{x}$Fe$_{11.5}$Si$_{1.5}$. In the present samples, a large $\Delta S_{\rm m}$ and a high $RC_{\rm eff}$ have been achieved simultaneously.