Microstructure and magnetocaloric effects of Mn1.2Fe0.8P0.6Si0.4B0.05 alloys prepared by ball milling and spinning methods

The Mn1.2Fe0.8P0.6Si0.4B0.05 alloys were prepared by ball milling and melt-spinning methods. The structure and magnetic characteristics of all samples were examined by X-ray diffraction, vibrating sample magnetometer and SEM. Results show that both the ribbon and bulk alloys can crystallize in a hexagonal Fe2P-type phase with some impurity phase. The lattice parameters, a and c, of Fe2P-type phase are 6.02960 Å, 6.03033 Å, and 3.42310 Å, 3.44431 Å for ribbon and bulk Mn1.2Fe0.8P0.6Si0.4B0.05 alloys, respectively. The Curie temperature increased by 20% from 165 K in bulk to 197 K in ribbon while thermal hysteresis and magnetic hysteresis decreased by 28% and 80% for ribbon sample, respectively. Moreover, the values of magnetic entropy change can be tuned from 15.7 J⋅kg−1⋅K−1 in bulk to 21.8 J⋅kg−1⋅K−1 in ribbon under 0–5 T, resulting in the effective refrigerant capacity (RCE) increasing from 238 to 286 J⋅kg−1. The nature of the phase transitions was studied through the Arrott plots, indicating that the samples undergo first-order ferro-paramagnetic phase transitions. The origin of magnetic hysteresis losses is also discussed deeply. Furthermore, this alloys with large magnetic entropy change could be an interest potential for future magnetic refrigeration applications.