Comparative study of magnetic properties and microstructure for as-cast and square-wave pulse current Joule annealed wires

We here report on a comparative study of the microstructure and magnetic properties of as-cast and SPCJA-ed Co-based wires for potential sensor applications. Experimental results indicate that both as-cast and SPCJA-ed wires exhibit typical amorphous feature. There also exists the enhanced local ordering degree of atomic arrangement and obvious transformation (maximum magnetic permeability and minimum saturation magnetization) of magnetic properties after SPCJA treatment, resulting from variation of magnetic moment exchange coupling and magnetic anisotropy by coactions of high-density pulsed magnetic field energy and thermal activation energy. Moreover, SPCJA treatment can drastically improve the GMI property of melt-extracted wires. GMI ratio [ΔZ/Z₀]_max of 166.07% and field response sensitivity ξ_max of 413.76%/Oe by more than 2.25 times and 1.73 times of as-cast wire at 5MHz. Therefore, the SPCJA-ed wire exhibits the improved GMI and magnetic properties at 5MHz∼10MHz in contrast to AC annealed wire, which is more suitable for GMI sensor applications working at low-applied-frequency and relatively low-working-magnetic field.