Magnetocaloric properties and magnetic refrigerant capacity of MnFeP1−xSix

Magnetic entropy change, ΔSM, and the refrigeration capacity, q, of MnFeP1−xSix have been examined. In accordance with the previous report, the compounds with 0.30 ⩽ x ⩽ 0.60 undergo a first-order magnetic transition near room temperature. The Curie temperature is increased linearly from 210 K to 360 K with increasing x from 0.30 to 0.60. The compounds display large thermal hysteresis. This hysteresis decreases with increasing x. We have carefully estimated ΔSM of the compounds with large thermal hysteresis from the Maxwell relation using the magnetization–temperature curves. It was found the peak values of ΔSM in a field change of 2 T is 7–13 J/K kg, which are much smaller than the values reported previously. On the other hand, the q values of the compounds over the temperature range 30 K were found to be 1.5 times as large as that of metallic Gd. These results demonstrate excellent magnetic refrigerant capacity of MnFeP1−xSix near room temperature. To expand the working temperature range of magnetic refrigerant materials, a design of a composite material is also proposed.

► Magnetic entropy change of MnFeP1−xSix was carefully studied.
► Magnetic entropy change in 0–2 T of the compounds is less than 13 J/K kg.
► In contrast, the refrigerant capacity is 1.5–2 times as large as that of Gd.
► A design for a composite material is discussed for practical application.