Abstract
Variation of electrical resistance in single-crystalline Ni50Mn50-xInx alloys (x=14-16) upon martensitic transformation was investigated. In Ni50Mn35In15 with T-m similar to 295 K, a negative magnetoresistance (MR) over 60% is attainable at moderate field strengths; in Ni50Mn34In16 with T-m similar to 190 K, the MR can exceed 70% over a temperature of approximately 100 K. The significant change in electric resistance upon martensitic transformation originates primarily from the altered electronic structure, while the large effect of a magnetic field follows its ability to manipulate the transformation in materials of low T-m and large Delta M/Delta S. The extremely large MR promises more innovative applications for these important alloys.