Enhanced magnetoresistance through magnetic-field-induced phase transition in Ni2MnGa co-doped with Co and Mn

We report the observation of giant negative magnetoresistance up to -46% at 60 kOe magnetic field in Ni1.68Co0.32Mn1.20Ga0.80 alloy, which is about 5 times larger than that reported in Ni-Mn-Ga alloys. The significant change in resistivity during martensitic transformation originates from the altered electronic structure due to the change of magnetic state. The magnetic-field-induced phase transition from partially antiferromagnetic martensite to ferromagnetic austenite is responsible for the enhanced magnetoresistance.