Study on magnetoresistance of Ni48Mn22Ga22Co4Cu4 microwires

Ni-Mn-Ga(Co, Cu) alloys have implicated magnetoresistance mechanisms as ferromagnetic shape memory alloys. The relationship between magnetoresistance and the martensitic transformation was researched. The magnetoresistance mechanism of microwires was related to the reorientation of martensite induced by magnetic fields. It is found that a negative MR of 4.81% was obtained in 20 kOe field in Ni48Mn22Ga22Co4Cu4 microwires with diameters of 0.28 mm at 327 K. The effect of diameters on the martensitic transformation observed in rho-T curves could be explained as the effect of rapid quenching during the preparation process, that smaller diameters wires have faster cooling rate and lower atomic order.