Magnetocaloric effects and transport properties of rare-earth (R = La, Pr, Sm) doped Ni 50-x R x Mn 35 Sn 15 Heusler alloys

Abstract The structural, magnetic, magnetocaloric, and transport properties of Ni 50 Mn 35 Sn 15 and Ni 50-x R x Mn 35 Sn 15 (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 L 2 1 austenite phase or mixture of L 2 1 and B2 at room temperature. We have observed that the ground state magnetization (T = 5 K) and the martensitic transition temperature (T M ) depended on the rare-earth ion. A drastic shift in T M by ∼62 K relative to the parent compound (T M  = 190 K) was observed for the Ni 49 LaMn 35 Sn 15 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 T M 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 T M and ΔH = 5T.