Variation of magnetoresistance in Ni2+xMn1-xGa with composition

The magnetoresistance (MR) of Ni2+xMn1-xGa (-1 <= x <= 0.35) ferromagnetic shape memory alloy shows a large increase in magnitude at room temperature (RT) with increasing x. For Mn2NiGa (x=-1), MR at 8 T is -0.2%, while for Ni2.35Mn0.65Ga (x=0.35), it is -7.3%. Thus, MR of Ni2+xMn1-xGa can be varied over one order of magnitude by changing composition (x). Considering that the Curie temperature (T-C) varies with x, the MR behavior in the austenitic phase is explained on the basis of the s-d scattering model. By fitting the MR at 8 Tin the austenitic phase for different x and T, a (T/T-C)(6) power law dependence is obtained. In contrast to the monotonic MR variation with x, the magnetization at RT is highest for Ni2MnGa (x=0) and decreases for both Ni and Mn excess compositions. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3259406]