Large magnetization change and magnetoresistance associated with martensitic transformation in Mn2Ni1.36Sn0.32Co0.32 alloy

In this paper we report on the realization of magnetic field-induced martensitic phase transformation in Mn-rich Heusler alloy Mn2Ni1.36Sn0.32Co0.32. The saturation magnetization of the austenite reached 111 emu/g at 70 kOe, which decreased rapidly to 8 emu/g upon transforming to martensite. This is attributed to the crystallographic distortion from cubic structure to tetragonal structure with c/a > 1, turning the Mn moments at B sites and D sites from parallel alignment to antiparallel alignment. A large magnetoresistance of 40% was observed through the field-induced transformation. The increase of conduction electrons accompanying this field-induced martensitic transformation is estimated to be 67%. These intriguing properties render the alloy a good candidate for applications in smart devices. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3607311]