Magnetocaloric effect, cyclability and coefficient of refrigerant performance in the MnFe(P, Si, B) system

MnFeP0.595Si0.33B0.075 has recently been presented as a top class magnetocaloric material combining a large magnetocaloric entropy change, a large temperature change, limited thermal hysteresis, and an enhanced mechanical stability. By providing practical rules to control the transition temperature in the MnFe(P, Si, B) system, we demonstrate that this new material was not a single composition and that a giant magnetocaloric effect (MCE) can be observed over a broad temperature range, a point of great interest for applications. As important prerequisite is the cyclability of the MCE. The thermal hysteresis and the recovery of the MCE during field oscillations have been addressed for MnFe(P, Si, B) materials. It is found that when the thermal hysteresis becomes about as large as the field induced shift of the transition, the MCE becomes partially irreversible and a strong decrease in the cyclic temperature change occurs. For an intermediate field change, typically 1 T, the limit for thermal hysteresis is about delta T-hyst approximate to 4K in the MnFe(P, Si, B) system. Finally, the interest of this material class for magnetic refrigeration is discussed in terms of the coefficient of refrigerant performance. (C) 2014 AIP Publishing LLC.