Phase transitions and magnetoresistance in Ni50Mn50-xInx Heusler alloys

The phase transitions and magnetoresistance in polycrystalline ferromagnetic Ni50Mn50-xInx (15 <= x <= 16.2) Heusler alloys were studied through ac susceptibility, magnetization, thermal expansion, and resistivity measurements in the temperature interval of 5-400 K. The temperatures of the martensitic transformations were found to be strongly dependent on In concentration and on the strength of the applied external magnetic field. We observed large magnetoresistance (MR) Delta rho/rho(o)approximate to-80% for x=16 at T approximate to 125 K and Delta rho/rho(o)approximate to-56% for x=15 at T approximate to 309 K for Delta H=5 T. In addition to large MR, the Ni50Mn50-xInx system exhibits ferromagnetic shape-memory effect and a large magnetic entropy change. Hence this system has potential to be a multifunctional applied material. (C) 2008 American Institute of Physics.