Characterization of thermal hysteresis in magnetocaloric NiMnIn Heusler alloys by Temperature First Order Reversal Curves (TFORC)

The temperature variant of the First-Order Reversal Curves (TFORC) technique has been applied to study the thermal hysteresis of two magnetocaloric Heusler alloys with slightly different compositions that are close to the stoichiometry Ni50Mn34In16. The similarity of the compositions causes the samples to have similar Curie temperature but different martensitic transition temperature and thermal hysteresis, leading to different features when analyzing the TFORC distributions due to the different relative distance between the two transitions. The asymmetry of the martensitic transformation upon cooling and heating has relevant effects on the TFORC distributions. The experimental results have been compared to the predictions of a model of the transformation, which allows to separate the contributions of the magneto-structural transformation and the thermomagnetic behavior of both martensitic and austenitic phases, allowing to determine the origin of the different features of the distributions.