Magnetocaloric effects and transport properties of rare-earth (R = La, Pr, Sm) doped Ni50-xRxMn35Sn15 Heusler alloys

The structural, magnetic, magnetocaloric, and transport properties of Ni50Mn35Sn15 and Ni50-xRxMn35Sn15 (x = 1 and R = La, Pr, Sm) compounds has been studied through X-ray diffraction (XRD), differential scanning calorimetry, and magnetization measurements. Analysis of the XRD data reveals that the compounds crystallize in the cubic L21 austenite phase or mixture of L21 and B2 at room temperature. We have observed that the ground state magnetization (T = 5 K) and the martensitic transition temperature (TM) depended on the rare-earth ion. A drastic shift in TM by ∼62 K relative to the parent compound (TM = 190 K) was observed for the Ni49LaMn35Sn15 compound. The compounds exhibit both inverse and normal magnetocaloric effects. Magnetic entropy change of 5.2 J/kg K (Sm), 12 J/Kg K (Pr), and 6 J/kg K (La) were found at TM for ΔH = 5T. Relative cooling power values of 267, 336, and 230 J/Kg were found at the Curie temperatures of the compounds with Sm, Pr, and La substitution, respectively. Significant magnetoresistance values were observed in these compounds, with the largest being −30% for the La substituted compounds at TM and ΔH = 5T