Investigation Of Giant Magneto-impedance Effect For Glass-Coated Co-rich Amorphous Wires

Giant Magneto-impedance (denoted as GMI) effect is discovered as one of new physical phenomena in 1990s. Due to its high sensitivity, lower saturation magnetic field, fast response and good stability in the magnetic field, GMI effect has a good potential application for magnetic sensors.Based on the measurement of GMI effect, the size of the wires and treatment process for GMI effect was extensively considered and a magnetic field sensor of amorphous wire by virtual instrumentation was designed in this thesis. This work laid a technological foundation for the development of practical micro-magnetic sensor.Having compared the different lengths and radius of Co-based amorphous glass-coated wires, the tested material which has more remarkable GMI effect was selected. At first, the long wires show a more remarkable effect than the short ones owing to the demagnetization. And then, the effect of the coating glass on GMI effect of amorphous wire was studied.After removing the glass coating, the residual quench-in stress arising from the difference in thermal expansion coefficients of the alloy and the glass was relaxed. Thus, this process led to change the magnetic domain. The changed magnetic domain structure of the circumference of anisotropy led to the GMI effect variation. Finally, we use direct current annealed the cast wires, and explored that the most appropriate annealing current density for this material is 200 A/cm2.With the combination of the virtual instrumentation and GMI effect of amorphous wire, a magnetic field sensor prototype was designed for the needs of weak magnetic field measurement. Our results show that the design give a guideline for the realization of micro-sensor application in the future.