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

• High performance and low cost Mn–Fe–P–Ge powders for magnetic cooling near RT.
• Maximum relative cooling power of 1138 Jkg−1 was observed in Mn1.1Fe0.9P0.79Ge0.21.
• High maximum magnetic entropy change and wide working temperature range near RT.
• Determine the critical composition for the crossover from 1st to 2nd order transition.
• Good agreement between experimental results and modeling by Landau theory.

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 ΔSM near room temperature in powder samples. With increasing Ge content, the magnetic transition temperature increases. Interestingly, large relative cooling power (RC) together with high ΔSM were obtained near room temperature in Mn1.1Fe0.9P0.79Ge0.21 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 Mn1.1Fe0.9P0.79Ge0.21 powders possess attractive magnetocaloric properties for commercial applications.