Large magnetocaloric effect near room temperature in Mn-Fe-P-Ge nanostructured powders

Mn-Fe-P-Ge alloys are attractive candidates for affordable and high performance magnetocaloric materials (MCM). The magnetocaloric effect (MCE), crystal structure and magnetic transition of Mn-Fe-P-Ge nanostructured powders were investigated with the aim of obtaining both high relative cooling power and large entropy change. In this work, the Ge content was tuned to obtain high ΔS_M near room temperature in powder samples. With increasing Ge content, the magnetic transition temperature increases. Interestingly, large relative cooling power (RC) together with high ΔS_M were obtained near room temperature in Mn_1.1Fe_0.9P_0.79Ge_0.21 powders, the RC value is much larger than previously reported values in Mn-Fe-P-Ge alloys. To model the magnetic transition and magnetocaloric behavior, Landau theory and a modified Arrott plot were utilized, good agreement was obtained between the theoretical model and the experimental results. Our results suggest that Mn_1.1Fe_0.9P_0.79Ge_0.21 powders possess attractive magnetocaloric properties for commercial applications.