First-Order Reversal Curve (FORC) Analysis of Magnetocaloric Heusler-Type Alloys

Abstract

The thermomagnetic hysteresis loops of a $\text{Ni}_{45.7}\text{Mn}_{36.6}\text{In}_{13.5}\text{Co}_{4.2}$ Heusler-type alloy exhibiting inverse magnetocaloric effect were studied with the help of first-order reversal curves (FORC). These have been measured using two different protocols (either upon heating or cooling the sample) and using different applied magnetic fields. For proper comparison, FORC distributions were shifted according to the field dependent center of the $M(T)$ hysteresis loop, which follows a linear trend. The qualitative behavior of FORC distributions remains the same, allowing their use for fingerprinting the transition, while there is a shift of their maxima along the hysteretic temperature axis and their distributions also get broader along the interaction temperature axis with increasing magnetic field. This was evidence that FORC distributions are dependent on the intensive variables temperature and field. As a consequence, it is necessary to obtain them for different temperatures and fields in order to accurately model the transition.