The Influence Of Various Annealing Methods On GMI Effect Of Amorphous Co_based Glass-covered Microwires

The giant magneto-impedance (GMI) effect is a phenomenon that there will be a giant change of the impedance of a ferromagnetic material when it is subjected to an external magnetic field. There are a lot of prospective applications (for example, in magnetic recording heads and sensor elements) because of its many advantages (high-sensitivity,quick response and low power consumption, and so on).A summary of research on GMI effect is generally presented in this thesis. Amorphous Co-based microwires are prepared by Taylor-Ulitovsky method. Different annealing methods are used to improve their properties. We study the soft magnetic properties and the asymmetrical GMI effect on annealing conditions and the exchange coupling between oxidation surface and nanocrystalline core.The main content is listed below:1. Preparation of Amorphous Co-based glass-covered microwires and these materials are preformed by Joule current and stress Joule annealing.(1) The soft magnetic properties would be improved after removal of the glass cover.(2) The optimal density of the Joule current is 2.0×10~7 A/m~2 and the best stress is 90 MPa. The soft magnetic properties improve with the increase of the density of current and the intensity of the stress if the density and stress are less than 2.0×10~7 A/m~2 and 90 MPa, then decease when current and stress continue to increase.2. Amorphous Co-based microwires are annealed in open air after glass coating remove.(1) The relationship between giant magneto-impedance effect and the annealing temperature and time is investigated. The results show that the sensitivity of GMI effect to magnetic field firstly increases then decreases with the annealing temperature and time. The maximum of GMI sensitivity was obtained in the samples annealed at 400℃for 9 hours.(2) It is realized that the exchange coupling interaction is the main reason of the AGMI and the improvement of soft magnetic properties of the wires.