Magnetocaloric Properties of Melt-Spun Fe–Ni–Mn–Ga Ribbons

The effects of Ni substitution for Fe on phase constitutions, Curie temperature T_C, and magnetocaloric properties of melt-spun Fe_50-xNi_xMn₂₅Ga₂₅ (x = 0, 1, 3, 5 and 7) ribbons have been investigated. X-ray diffraction results show that the main phase in the Fe_50-xNi_xMn₂₅Ga₂₅ (x = 0-7) alloy changed with the increase of Ni content from FCC structure for x = 0 into B2 structure for x = 1-7. Besides, the magnetic phase exhibits phase transition of ferromagnetic into paramagnetic state with increasing temperature for the samples with B2-type structure. The Curie temperature T_C of these ribbons varies in the temperature range of 232-257 K. The peak values of the maximal magnetic entropy change, -ΔS_M^max, are about 1.4-1.6 Jkg/K for Ni-substituted ribbons at a maximum applied field of 30 kOe. On the other hand, the relatively broader temperature range at the half maximum of ΔS_M peak (~ 90 K), low-cost and nontoxic elements make Fe-Ni-Mn-Ga-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature.