The scaling and universality of conventional and inverse magnetocaloric effects in Heusler alloys

We report a comparative study of the universal behaviors of conventional and inverse magnetocaloric effects (CMCE and IMCE, respectively) that coexist in Heusler alloys of Ni50Mn50-xSnx (x similar to 13, 14) and Ni50-xPrxMn37Sn13 (x similar to 1, 3). In contrast to CMCE associated with a first-order phase transition (FOPT), we show that it is possible to construct a universal master curve to describe the temperature dependence of magnetic entropy change DSM(T) in different applied fields without rescaling the temperature axis for IMCE associated with FOPT. This universal behavior is shown to be different from that observed for CMCE associated with a second-order phase transition. The proposed universal curves provide an effective method of extrapolating DSM of materials associated with CMCE and IMCE in any range of temperatures and magnetic fields, giving useful guidance on the development of active magnetic refrigerants. (C) 2013 AIP Publishing LLC.