Magnetic properties and magnetocaloric effect in Ni-Mn-Sn alloys

Magnetic and magnetocaloric properties in Ni50Mn50−xSnx alloys with wide range of the Sn-concentration (x=0-40) were investigated. The alloys were prepared by arc-melting and subsequently annealing at 850 °C for 4 h. The X-ray diffraction analyses manifest the formation of the crystalline phases (Ni2MnSn, NiMn, Ni3Sn2, Mn3Sn, and MnSn2) in the alloys with various compositions and fabrication conditions. With increasing x, the saturation magnetization first increases from near zero (at x=10) to above 40 emu/g (at x=20) and then decreases to below 10 emu/g (at x=40) for both the as-melted and annealed cases. The martensitic-austenitic transition was observed in the alloys with a narrow range of x (13-15). The magnetic transitions in the alloy can be controlled by changing Sn-concentration. The alloy reveals both the positive and negative entropy changes with quite large magnitude (∆Sm>1 J/kg K with ∆H=12 kOe) with appropriate compositions and annealing conditions.