Analysis Of Giant Magneto-Impedance Effect And Technical Magnetization Based On Amorphous Co-Based Wire

The study is based on diameterΦ25μm Co-based amorphous wires in this paper. After vary heat treatments, the GMI effect and the soft magnetism property of the amorphous wires were analyzed.The results show that conventional heat treatment plays great roles on the impedance of the specimens, furthermore the giant magneto-impedance (GMI) effect and the soft magnetic property of the specimens had been obviously improved after appropriate heating treatment. When testing the silk specimen annealed 25minutes, the impedance 2195? and GMI ratio 730% were observed. Longitudinal heat treatment in magnetic field can eliminate magnetism anisotropy of the amorphous wires, and then asymmetry giant magneto impedance (AGMI) can be obtained. When playing heat treatment on the amorphous wires, adding proper biasing magnetic field can further improve the GMI effect, linearity and sensitivity of the specimens, furthermore the soft magnetic property was optimized. Among the specimens, the one annealed 20minutes at 0.15T, the GMI ratio reached to 1230%, and the sensitivity of the magnetic field reached to 180%/Oe.The variations of excitation frequency and applied magnetic field have effect on impedance, which has been studied. The result shows that Co-based amorphous wires exhibit better GMI effect at high frequency than at lower frequency. Therefore, in its practical application the operating frequency should be high. DC magnetic field is applied to changing the magnetic conductivity, and then changes the skin depth to influence the impedance of the materials, External magnetic field can significantly influence the effective magnetic conductivity, which is the prime reason generating the GMI effect.The circular magnetic permeability and demagnetization energy were calculated. The changing of circular magnetic permeability with the changes of external magnetic field shows the circular coercivity mechanisms adapted to specimens with vary domain structures are different. Demagnetization field and anisotropy field influence the domain structure of specimens together, so that impedance of the specimens would be changed. When testing the specimens with high saturation magnetization intensity, great demagnetization energy was detected as external magnetic field equaled to saturated magnetic field, and obvious GMI effect has been observed.