Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device.

The magnetocaloric first order material MnFe(P,As) is a candidate for room temperature magnetic refrigeration. However, these materials have intrinsic hysteresis and the impact on the refrigeration performance has not yet been thoroughly investigated in the literature. Here, the magnetocaloric effect (MCE) and the thermal hysteresis are studied using vibrating sample magnetometry. The influence on actual refrigeration performance is investigated with an established active magnetic regenerator (AMR) test device (Bahl et al., 2008), utilizing a flat plate regenerator of a single Curie temperature material. We find that the MCE curves are shifted 1.5 K when comparing heating and cooling the material, while the maximum MCE remains constant. The width of the MCE curve peak is seen to increase 0.3 K when cooling compared to heating. These results are confirmed by experiments on the AMR test device.