Specific heat capacity of undercooled magnetic melts

Abstract

The specific heat capacities of (Co, Ni, Fe)–Pd alloys were determined in the crystalline and metastable undercooled liquid state using differential heat flow calorimetry. Applying the melt fluxing technique, the liquid alloys were undercooled by more than 330 K below their respective liquidus temperatures. For Co100−xPdx (x=20 and 25 at. %) the undercooled liquid approached the temperature regime of the ferromagnetic crystalline phase. The heat capacity of the liquid samples as a function of temperature shows a cusplike rise in the vicinity of the Curie temperature of the solid state. For (Fe, Ni)–Pd alloys, where the Curie temperatures are far below the crystallization temperatures achieved in undercooling experiments, an almost constant specific heat at the same levels of undercooling is observed. These results, together with recent magnetization measurements, indicate the existence of a magnetic phase transition in the undercooled liquid state of the Co–Pd alloys.