Effect of seven-layered martensite in Ni-Mn-Ga magnetic shape memory alloys

Abstract

The off-stoichiometric Ni_50.9Mn_26.7Ga_22.4 polycrystalline alloy is prepared by using arc-melting furnace. The effect of annealing on the microstructure and the magnetic properties of Ni_50.9Mn_26.7Ga_22.4 alloy has been investigated. It exhibits single phase of seven-layer modulation with good crystallinity of orthorhombic structure. The scanning electron microscopy studies are employed at room temperature to analyze the twin formation in 7M martensitic structure and the stripe like fine martensitic bands observed. The residual stresses have been observed inside the sample while crushing the test sample, which exhibits the broadened peaks. At room temperature, the alloy showed the ferromagnetic hysteresis behavior with soft magnetic nature.