Tuning the magnetic entropy change of Ni_50-xMn_35+xIn₁₅ alloys by varying the Mn content

Magnetocaloric effect associated with the first-order martensitic transition (T_M) is investigated in polycrystalline Ni_50-xMn_35+xIn₁₅ alloys with varying Mn content but fixing In content. It is found that when Mn content reaches x=3, a field-induced metamagnetic transition takes place. An external magnetic field can reduce T_M to a lower temperature at a rate of 3.5 K/T, thereby yielding a large magnetic entropy change ΔS near room temperature. The ΔS magnitude attains to 33 J/kg K under a magnetic field of 5 T at 285 K for the sample with x=3, while the temperature span of the ΔS peak can reach 15 K because of the reduction in T_M by the external magnetic field. The calculated refrigerant capacity reaches 279 J/kg for the sample with x=3. These values of the magnetocaloric parameters suggest that these alloys are suitable candidates for magnetic refrigerants.