Large Magnetoresistance and Magnetic Field Induced Strain in Ni42.8Co7.7Mn38.8Al10.7 Heusler Alloy at Room Temperature

Large magnetoresistance and large magnetic field induced strain are observed in polycrystalline Ni42.8Co7.7Mn38.8Al10.7 Heusler alloy. The martensitic transformation from ferromagnetic austenite to weak-magnetic martensite is realized in the alloy around the room temperature. A magentoresistance of -45% and magnetic field induced strain up to -500ppm are observed under the magnetic field of 90kOe. The evolution of the topography and magnetic domain is measured by magnetic force microscopy under different magnetic fields. Dramatic changes in magnetic domain structures are observed and discussed in the martensitic transformation process. The magnetic field induced reverse martensitic transformation should account for the large magnetoresistance and magnetic field induced strain. The results indicate the potential application of Ni42.8Co7.7Mn38.8Al10.7 alloy in magnetic multifunctional materials.