Impact of thermally induced stress gradient on magneto-impedance sensitivity of As-quenched and Joule annealed microwires

The investigation addresses the dependence of rapidly quenched (Co 94 Fe 6 ) 72.5 Si 12.5 B 13 Cr 2 microwire diameters on their phase transformation evidenced during devitrification and consequent giant magneto -impedance (GMI) behavior. Phase segregation / nucleation in thicker microwires as compared to thinner ones were detected through thermal studies. In addition to such nucleation, the stress effect was more pronounced in thinner microwires as evidenced from GMI output. Structural relaxation through Joule annealing further enhanced the properties. Appropriate choice of operating frequency, alternating current and Joule heating current density vis`a-vis microwire diameter is essential for sensor design.