Magnetocaloric effects in Mn1.35Fe0.65P1-xSix compounds

The structural and magnetocaloric properties of Mn1.35Fe0.65P1-xSix compounds are investigated. The Sisubstituted compounds, Mn1.35Fe0.65P1-xSix with x = 0.52, 0.54, 0.55, 0.56, and 0.57, are prepared by high-energy ball milling and the solid-state reaction. The X-ray diffraction shows that the compounds crystallize into the Fe2P-type hexagonal structure with space group P (6) over bar 2m. The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x = 0.52 to 296 K for x = 0.56. The isothermal magnetic-entropy change of the Mn1.35Fe0.65P1-xSix compound decreases with the Si content increasing. The maximal value of the magnetic-entropy change is about 7.0 J/kg.K in the Mn1.35Fe0.65P0.48Si0.52 compound with a field change of 1.5 T. The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples. The thermal hysteresis of the compound is less than 3.5 K. The maximum adiabatic temperature change is about 1.4 K in the Mn1.35Fe0.65P0.45Si0.55 compound with a field change of 1.48 T.