Magnetic Properties And Giant Magneto-Impedance Effect In FeCuNbSiB Nanocrystalline Ribbons

The giant magneto-impedance (GMI) effect is a newly discovered physical effect in amorphous soft magnetic alloys,which is referred to the sensitive changes of impedance with applied external magnetic field. Recently,The giant magneto-impedance effect in magnetic materials has attracted great attentions for its high sensitivity,small dimension,rapid response and less energy consumption for GMI sensors application compared with MR,GMR and magnetic fluxgate sensors. In this thesis,we choose the amorphous and nanocrystalline Fe-based alloys which have comprehensive soft magnetic properties as research objects,and excellent GMI effect is shown through certain heating treatment optimization,shape and dimension optimization. At the same time,the magnetic properties,microstructure and the resulting changes in the corresponding GMI effect are studied.The main content and innovative results are generalized as follows:1. This thesis provides a comprehensive research of the GMI in GMI materials,encompassing fundamental understanding of the GMI phenomena , the measuring parameters (e.g.,ac current,dc magnetic field,and frequency) that affect the measured value of GMI , the properties and processing techniques for the production of nanocrystalline GMI materials.2. Test the manetic materials with the VSM and Agilent E4194A RF impedance/materials analyzer.3. Single-layer and five-layer structure including line structure and meander structure of nanocrystalline FeCuNbSiB ribbons are prepared by photolithography,etching,polishing electroplating. The microfabrication process is optimized based on performance and experiment requirements.4. Analize the heating treatments on the GMI effect. GMI effect in the above two structure of nanocrystalline FeCuNbSiB ribbons is systematically and comparatively studied. Their impedance changing trends in GMI effect are similar. But the impedance change of the meander five-layer structure is much larger than that of the single-layer structure,and the frequency at which the maximum change of the meander five-layer structure GMI appears,is much lower. This behavior is very useful for application. Several factors that affect GMI are analyzed and the underlying physical origins of GMI are explained.