Magnetic and magnetocaloric properties of Ni-50-xCuxMn39Sn11 alloys

The effect of Cu substitution on the martensitic transition and magnetocaloric properties of arc-melted Ni-50-xCuxMn39Sn11 (x = 6 and 7) Heusler alloys are investigated by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy and magnetic measurements. According to XRD patterns, while Ni44Cu6Mn39Sn11 alloy exhibit orthorhombic structure, Ni43Cu7Mn39Sn11 alloy crystallize cubic L2(1) structure at room temperature. The substitution of Cu for Ni leads to decreasing on the martensitic transition temperatures to lower values. The magnetic entropy changes calculated from M(T) curves, for avoiding hysteresis losses in the vicinity of the martensitic transition region, by using Maxwell relation. The maximum magnetic entropy change, Delta S-M is found 11.0 J kg(-1) K-1 for Ni43Cu7Mn39Sn11 alloy around the martensitic transition region, which is nearly twice as large as the Ni44Cu6Mn39Sn11 alloy under the magnetic field changing from 0 to 2 T.