Magnetostrictive and shape memory properties of Heusler type Co₂NiGa alloys

We have researched and developed a new Heusler-type ferromagnetic shape memory alloy Co₂NiGa, which has large magnetostriction caused by the magnetic-field-induced re-arrangement of martensite twin. The ribbon samples produced by rapid-solidification melt-spinning method show strong texture and large magnetostriction ε of about 110 × 10^-6 for an applied magnetic field of 800 kA·m^-1 at room temperature. When increasing temperature, the martensite phase of Co_52.4Ni₂₂Ga_25.6 and Co_52.1Ni_26.1Ga_21.8 ribbons disappears at about 390 K and 330 K, respectively, where the drastic shape recovery arises. Some of the ribbons have good ductility and are not broken even after bending to an angle of 180, indicating that the Co₂NiGa system has a possibility of new ferromagnetic shape memory material with good ductility.