Investigation On The Giant Magneto-impedance Effect Based On The Soft Magnetic Materials

Magnetic sensors are widely used in various fields of medical equipment,industrial manufacturing,aerospace,quality inspection,etc.The magnetic sensors based on giant magneto-impedance(GMI)effect with many advantages of high sensitivity,small size,easy integration and low price have great application prospect.Since the GMI effect of the Co-based amorphous was discovered,many researches had been done on how to improve the GMI effect of samples based on the skin-effect in low frequency band and developing new GMI materials correspondingly.There were few investigations on GMI effect based on FMR effect in the high frequency band.In this paper,the GMI effect has already been researched based on the FMR effect mainly.The main results are as follows:1.Firstly,the magneto-impedance generation mechanism in MHz frequency band and structural optimization methods based the traditional eddy current have been studied.Based on the comparative analysis of the results of GMI signal by diagonal measurement and off-diagonal measurement,the influence of different winding methods on the off-diagonal GMI effect of amorphous has been studied.The experimental results showed that the GMI effect of the amorphous can be significantly enhanced by increasing the number of the amorphous wound in the copper coil or by making the amorphous fold back to form series connection.2.Then we studied the high frequency GMI effect of amorphous based on the FMR effect.Amorphous was used to replace part of the microstrip transmission line.The relationship between the transmission coefficient and impedance of the amorphous wire or the microwave frequency and the external magnetic field has been obtained through the high frequency reflection transmission test.Theoretically,due to the FMR effect,the magnetic conductivity of the amorphous in GHz band responds strongly with the external magnetic field,which can improve the equivalent impedance of microwave circuit.However,the damping coefficient of amorphous materials is larger and the resonance line width is wider,so the linearity of GMI results is more poor.3.The FMR phenomenon and GMI effect of yttrium iron garnet(YIG)with smaller damping factor and narrower resonance linewidth have been investigated in detail.And the test fixture was replaced with coplanar waveguide.Since YIG is an insulating material,there was no need for any connection between the sample and the test fixture.The experimental results show that YIG material will produce intense GMI effect near the magnetic field and frequency of FMR,which can reach 200-1120%.Through comparison,it is found that the YIG thin film material has higher GMI effect and better linearity,so it is more likely to be used in GMI sensor.