Field-driven structural phase transition and sign-switching magnetocaloric effect in Ni–Mn–Sn
Depending on the starting equilibrium temperature, the application of a magnetic field on a sample of Ni–Mn–Sn produces sample heating or cooling during adiabatic experiments. The competition between endothermal and exothermal effects is observed close to the martensite-to-austenite magnetostructural phase transition. A model assuming the coexistence of two phases and a field dependence of their volume allows to compute the evolution of entropy and heat capacity during the phase transition. The correct fitting of the results suggests that the field-induced reduction of the martensite-to-austenite transition temperature is responsible for the observed sign switching of the magnetocaloric effect.
The following article appeared in Applied Physics Letters 91 (2007): 131904 and may be found at http://dx.doi.org/10.1063/1.2790829.