Magneto-transport and magnetic properties of Ni-Mn-Ga

Abstract

We report a detailed investigation of the magneto-transport and magnetic properties of Mn excess Ni-Mn-Ga using the resistivity and magnetization measurements. Magnetoresistance (MR) has been measured in the ferromagnetic state for different compositions in the austenitic, premartensitic and martensitic phases. With Mn doping in NiMnGa, a decrease in magnetization and MR has been found, since the doped Mn atoms in Ni position are in the antiferromagnetic configuration with the Mn atoms in Mn position. MR for the parent stoichiometric composition NiMnGa varies almost linearly with field in the austenitic and pre-martensitic phases, and shows a cusp-like shape in the martensitic phase. This has been explained by the changes in twin and domain structures in the martensitic phase. Hysteresis in the heating and cooling cycles is a characteristic of the first order nature of the martensitic phase transition.