Influence of H and Extra La on Magnetocaloric Effect of La $_{0.5 + x}$ Pr $_{0.5}$ Fe

Magnetic properties and magnetocaloric effect were investigated on La_0.5+xPr_0.5Fe_11.4Si_1.6H_y (x=0, 0.1, 0.2) melt-spun ribbons. It was found that NaZn₁₃-type phase could be obtained easily owing to that the segregation of α-Fe phase was suppressed obviously by adding appropriate amount of La after a short time annealing for melt-spun ribbons. For the La_0.6Pr_0.5Fe_11.4Si_1.6H_y ribbons, the Curie temperature was adjusted dramatically from low temperature of 193 K to room temperature of 321 K due to the interstitial hydrogen adsorption. With La content increasing, Curie temperature was slightly increased; the magnetic hysteresis was reduced, while a large magnetic entropy change remained. The maximum magnetic entropy change (- ΔSM) is 33.8 J/(kg·K) for La_0.6Pr_0.5Fe_11.4Si_1.6 while that of La_0.6Pr_0.5Fe_11.4Si_1.6H_y is 19.6 J/(kg·K) in a magnetic field change of 5 T. It is shown that rapid quenching to make LaFe_13-xSi_x alloys is more cost effective than arc melting method by reducing annealing time substantially. High magnetic entropy change and low magnetic hysteresis were obtained by adding extra La and the Curie temperature was tuned to near room temperature by interstitial atom H. This work indicated that La_0.6Pr_0.5Fe_11.4Si_1.6H_y was a promising magnetic refrigeration material near room temperature.