Structural investigation of the crossover in the magnetic transition of Mn-Fe-P-Ge magnetocaloric powders

Mn-Fe-P-Ge alloys are promising candidates as rare earth free, high performance, magnetocaloric materials (MCM) for magnetic cooling applications. The magnetocaloric properties, crystal structure and phase transition of Mn-Fe-P-Ge alloys were investigated. High values of the relevant magnetocaloric properties; i.e., relative cooling power and entropy change were obtained in these alloys. However, the nature of the magnetic transition which gives rise to these attractive properties is still unclear. Hence, we studied, by X-ray characterization, the effect of varying Ge content on the crossover from a first order to a second order phase transition. This crossover was found to be related to the initial lattice parameter of the parent phase. The transition temperature was also influenced by the lattice parameter, which is, in turn, related to Ge content.