Stress-assisted large magnetic-field-induced strain in single-variant Co-Ni-Ga ferromagnetic shape memory alloy.

The magnetic anisotropy and the magnetic-field-induced strain (MFIS) in a single-variant Co(47.5)Ni(22.5)Ga(30.0) ferromagnetic shape memory alloy (FSMA) have been investigated. From the magnetization curves for the single crystal, the hard c-axis was confirmed, and the uniaxial magnetic anisotropy constant K(u) at 300 K was evaluated to be -1.07 × 10(6) erg cm(-3) for the single-variant Co(47.5)Ni(22.5)Ga(30.0) martensite phase. The magnitude of compressive shear stress for the variant rearrangement was estimated to be 6.0-7.5 MPa from the stress-strain curves. An assisted stress τ(assist) of 6.0 MPa was applied before applying a magnetic field, and then a magnetic stress τ(mag) of 0.3 MPa was added. As a result, a large MFIS of about 7.6 % was obtained at room temperature in the martensite phase of the single-variant Co(47.5)Ni(22.5)Ga(30.0).