Magnetocaloric effect in high Ni content Ni52Mn48−xInx alloys under low field change

Ni-rich Heusler alloys Ni₅₂Mn_48−xIn_x (x=15.5, 16 and 16.5) were prepared by the arc melting method. X-ray diffraction analysis revealed that the martensite has orthorhombic structure (S.G. Pmm2) at room temperature. The only alloy with x=15.5 has structural transmission from martensite to austenite without any magnetic transmission. The temperature dependence and the field dependence of the magnetization measurement indicated that the magnetization increased with the decreasing of the concerntration of Mn. The lesser the Mn atoms located in the In atom sites, the weaker the total AFM interaction in the system. Giant entropy changes ΔS_M(T, H) were found in Ni₅₂Mn_48−xIn_x alloys with the maximum ΔS_M value of 22.3 J kg K for the sample with x=16.5 at 270 K under the magnetic field change of 1.5 T.