文摘

The present work is devoted to investigating the microstructure, magnetism and magnetocaloric effects of Si- and Mn-rich FeMn(P,Si) alloys. The Mn-substituted alloys with Fe_2–xMn_xP_0.4Si_0.6 (x = 1.25, 1.30, 1.35, 1.40, 1.45 and 1.50) were prepared by high-energy ball milling and solid-state reaction. Experimental results show that the alloys crystallized into a majority Fe₂P-type hexagonal structure, coexisting with minor amounts of (Mn,Fe)₃Si and (Mn,Fe)₅Si₃ phases. The Curie temperature decreased linearly from 321 to 266 K with increasingMn content from1.25 to 1.50 in Fe_2–xMn_xP_0.4Si_0.6 alloys. The first-order magnetic phase transition became weakened and the second-order magnetic phase transition became dominated with increasing Mn content. Fe_0.75Mn_1.25P_0.4Si_0.6 alloy presents a maximum isothermal magnetic-entropy changes of 7.2 J (kg K)–1 in a magnetic field change of 0–1.5 T. The direct measurement shows that Fe0.7Mn1.3P0.4Si0.6 and Fe_0.65Mn_1.35P_0.4Si_0.6 alloys exhibit a maximum adiabatic temperature change of 1.8 K in a magnetic field change of 0–1.48 T. The thermal hysteresis for all alloys is less than 4 K. These experimental results reveal that Fe_2–xMn_xP_0.4Si_0.6 alloys could be a candidate material for magnetic refrigeration.