The spike in the relation between entropy change and temperature in LaFe11.83Si1.17 compound

LaFe11.83Si1.17 compound shows a first-order transition from paramagnetic to ferromagnetic state. When measurement is carried out from low to high temperature in an increasing field, there is a spike of 51 J/kg K at 174.8 K, followed by a plateau of 20 J/kg K in the curve of entropy change versus temperature determined by the Maxwell relation. However, the nature of the spike is fictitious, which is caused by an obvious superheat of the ferromagnetic state when the Maxwell relation or the Clausius-Clapeyron equation is used to evaluate the entropy change.