Critical behavior, magnetic and magnetocaloric properties of melt-spun Ni50Mn35Sn15 ribbons

Microstructure, structural and magnetic phase transitions of the melt spun Ni50Mn35Sn15 ribbons have been examined by means of scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and magnetic measurements. The melt spun ribbons exhibit a single phase cubic L2(1) austenite structure at room temperature with a space group Fm-3m, and lattice parameter a = 5.956 angstrom. The DSC results reveal the first order reverse and forward martensitic transition (M-s = 147.4 K, M-f = 133.7 K, A(s) = 155 K and A(f) = 171 K) with a thermal hysteresis of about 21.3 K around the martensitic transition between heating and cooling. The thermomagnetic measurements show that the melt spun ribbons undergo a second order magnetic transition at a Curie temperature T-C = 310 K and a first order martensitic transition at T-M = 160 K. The critical behavior associated with the magnetic phase transition has been investigated through the isothermal magnetization measurements around T-C. The critical exponents have been estimated by several methods such as the modified Arrott plots, Kouvel-Fisher method and critical isothermal analysis. The critical exponents values beta = 0: 456, gamma = 0: 88 and delta = 2: 929 are close to those predicted from the mean field model revealing a dominated long-range order of magnetic interactions. For an applied magnetic field of 5 T, the maximum magnetic entropy change (Delta S-Mmax) and the relative cooling power (RCP) values around T-C are of about 2.105 J/kg.K and 132.5 J/kg, respectively. The melt-spun Ni50Mn35Sn15 alloy is a good candidate for magnetic refrigeration near room temperature. (C) 2017 Elsevier B.V. All rights reserved.