Magnetoelastic coupling induced magnetocaloric property variations in Ni-doped (Mn, Fe)2(P, Si) alloys

This study investigated MnFe0.95-xNixP0.5-ySi0.5+y (0.01 ≤ x ≤ 0.16, −0.05 ≤ y ≤ 0.1) alloys prepared by arc melting. The alloys were crystallized in a typical Fe2P-type hexagonal main phase. They exhibited strong coupling between lattice variation and magnetic transition, which is the major factor in the large magnetocaloric properties. The effects of coupling were observed from two perspectives: Fe-Ni substitution for transition temperature tuning and P/Si ratio for reducing the amount of expensive P alloy. For the Fe - Ni substitution, the transition temperature decreased by about 7.8 K per 0.01 Ni contents (x). In the case of the P/Si ratio control, a secondary phase was generated based on the increase in Si content. The alloys showed maximum magnetic entropy change (∆SMmax) ranging from 8.65 to 17.22 J kg−1 K−1 for the applied magnetic field 2 T in the temperature range from 214 K to 335 K. For the MnFe0.91Ni0.04P0.45Si0.55 alloy with a low P/Si ratio, the ∆SMmax was 15.32 J kg−1 K−1 for the applied magnetic field 2 T at 304 K close to room temperature. This demonstrates that the alloys with large magnetocaloric properties in this research are competitive to other known magnetic refrigeration materials.