| Recently, a large increase of interest has been concentrated on amorphous materials, for its technological applications in acousto-magnetic electronic article surveillance(EAS) system, and illustrate a good market prospect. A summary of research on EAS system is presented in this thesis. Amorphous Fe24Co11.82Ni47.3 Si1.47B15 ribbons were prepared. Then, they are annealed at different conditions. The Magneto-acoustic properties have been investigated. 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. The phenomenon has attracted a great deal of interest because of its prospective applications in magnetic recording heads and sensor elements. The GMI enhancement utilizing the magneto-mechanical resonance was investigated. The action mechanism and the optimal enhancement conditions were also discussed. The main results are listed as below.The amorphous Fe24Co11.82Ni47.3Si1.47B15 ribbons used for magnetomechanical electronic article surveillance system were prepared successfully. Then, they are annealed at different conditions to improve their response performance. The influence of annealing condition on the ribbons performance has been investigated. Results show that the highest resonance amplitude in the ribbon is obtained annealing at 340℃. It is favor of improving acoustic magnetic properties of ribbons when the annealing magnetic field is perpendicular to the ribbons surface or the press stress was used. Increasing ribbon thickness is unfavorable to improve resonance. The transverse magnetic structures were produced in the ribbon by pressure stress annealing, magnetic moment rotation is dominant in magnetization process, and the corresponding resonance is better.Longitudinally driven Giant Magneto-Impedance effect in amorphous magnetostrictive ribbons was measured. Experimental results showed that the ribbons were excited to magneto-mechanical resonance by magnetostrictive effect. When the impedance measurement frequency swept around the resonance frequency of the ribbons, and the GMI effect was significantly enhanced around the resonance frequency. The stronger of the magnetomechanical coupling, the higher of the maximal MI ratio, the maximal GMI ratio of 1532% was obtained in the sample annealed at 340℃ under transverse magnetic field. The results are explained in terms of the magnetomechanical coupling and the magnetomechanical resonance of the magnetostrictive materials. The parameters that influence the performance of acousto-magnetic label can be further calculated to obtain acousto-magnetic label with optimal properties. |
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