Abstract
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 ξmax 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.
Highlights
Recent investigations attracted much interest and indicated the novel giant magnetoimpedance (GMI) Co‐based amorphous microwires are the excellent candidate materials for the weakly magnetic field detection of potential GMI sensor applications[1,2]
Zhou et al.[8] investigated that the effect of AC Joule-heating annealing for melt-spun CoFeSiB amorphous ribbon on GMI property, influencing the easy direction magnetization, magnetic anisotropy and domain structure, and their [ΔZ/Z0]max increased to about 180% at 900kHz for special annealing conditions of 30 min and an AC current density of 2.8×107 A/m2
Indicate that the microstructure of wires entirely consists of once the frequency decreases below 50Hz, the improvement amorphous structure before and after square-wave pulse current Joule annealing (SPCJA)
Summary
Recent investigations attracted much interest and indicated the novel giant magnetoimpedance (GMI) Co‐based amorphous microwires are the excellent candidate materials for the weakly magnetic field detection of potential GMI sensor applications[1,2]. Compared with rotating water‐spinning and glass-covered melt-spinning techniques, melt-extracted microwire exhibits higher solidification rate and unique super-soft magnetic properties[3,4,5]. There exists an important trend for choosing more sensitive GMI materials: exploring novel magnetic microwires with enhanced GMI and magnetic properties. This final purpose of melt‐extracted Co-based amorphous microwires can be realized by using some efficient Joule annealing techniques, especially alternating current according to the special geometric shape[6,7]. Sinha et al.[9] observed [ΔZ/Z]max of CoMnSiB glass-coated microwire increased from 66% of as-cast to 129% after short-duration PC annealing with amplitude of 100 mA, due to the increase of outer shell
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