Searching the conditions for a table-like shape of the magnetic entropy in the magnetocaloric LBMO_2.98/LBMO_2.95 composite

Abstract.

The conditions to obtain a table-like behavior of the entropy change, on the composite system $(LBMO_{2.98})_{1-x}/(LBMO_{2.95})_{x}$, have been investigated from the isothermal magnetic entropy change versus temperature curves $\Delta S(T)$ of La_2/3Ba_1/3MnO_2.98 and La_2/3Ba_1/3MnO_2.95 materials. The latters are characterized by Curie temperatures ($T_{C}$) values (310 K for La_2/3Ba_1/3MnO_2.98 and 292 K for La_2/3Ba_1/3MnO_2.95 around room temperature. The temperature dependence of the isothermal magnetic entropy change $\Delta S(T)$ has been calculated for the composite system with $0 \le x \le 1$ . The optimum magnetocaloric effect (MCE) properties, i.e., a $\Delta S(T)$ curve with table-like shape, have been found in the temperature interval of 293-309 K for the composite with $x = 0.48$ at 1 T. The $\Delta S(T)$ of the composite comes close to a constant value of 1.73(7)J/(kg ·K). A large refrigerant capacity value of $\sim 66.4(9)$ J/kg is obtained in a wide temperature span over 16 K. This composite can be used as the working material in the Ericsson-cycle magnetic regenerative refrigerator. These results make the $(LBMO_{2.98})_{0.52}/(LBMO_{2.95})_{0.48}$ system a promising material for practical magnetic refrigeration using a lower field (1 T), which is much easier to generate by permanent magnets, than higher fields, like 2 T.