Variation of magnetoresistance in Ni2+xMn1−xGa with composition

Abstract

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 (TC) 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 T in the austenitic phase for different x and T, a (T/TC)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.