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Electromagnetic analysis of gmi effect in sandwich structured films

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Journal of Shanghai University(English Edition) 2006年第4期10卷 357-361页

作者：黄灿星刘龙平赵振杰马学鸣 Department of Physics East China Normal University Shanghai 200062 P.R. China

A model of giant magneto-impedance （gmi） effect in sandwich-structured film has been proposed based on the superposition principle of electromagnetic field. The expression of impedance is derived in the frames of electrodynamics and ferromagnetism. Electromagnetic interaction between the inner layer and outer layer is discussed. Numerical simulation is conducted and the results show that the conductivity of the inner layer is much larger than that of the outer ferromagnetic layer. The skin effect and the maximum gmi effect of the sandwich film may appear at a much lower frequency compared to that of monofilm. The computational results agree with experimental data.

关键词： gmi effect electromagnetic interaction sandwich structured film.

Giant magneto-impedance sensor with working point selfadaptation for unshielded human bio-magnetic detection

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Virtual Reality & Intelligent Hardware 2022年第1期4卷 38-54页

作者： Changlin HAN Ming XU Jingsheng TANG Yadong LIU Zongtan ZHOU College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410072China

Background Compared with traditional biomagnetic field detection devices,such as superconducting quantum interference devices(SQUIDs)and atomic magnetometers,only giant magneto impedance(gmi)sensors can be applied for unshielded human brain biomagnetic detection,and they have the potential for application in next-generation wearable equipment for brain-computer interfaces(BCIs).Achieving a better gmi sensor without magnetic shielding requires the stimulation of the gmi effect to be maximized and environmental noise interference to be ***,the gmi effect stimulated in an amorphous filament is closely related to its working point,which is sensitive to both the external magnetic field and the drive current of the *** In this paper,we propose a new noise reducing gmi gradiometer with a dual-loop self-adapting *** reduction is realized by a direction-flexible differential probe,and the dual-loop structure optimizes and stabilizes the working point by automatically controlling the external magnetic field and drive *** dual-loop structure is fully program controlled by a micro control unit(MCU),which not only simplifies the traditional constant parameter sensor circuit,saving the time required to adjust the circuit component parameters,but also improves the sensor performance and environmental *** In the performance test,within 2 min of self-adaptation,our sensor showed a better sensitivity and signal-to-noise ratio(SNR)than those of the traditional designs and achieved a background noise of 12 pT/√Hz at 10 Hz and 7pT/√Hz at 200 *** To the best of our knowledge,our sensor is the first to realize self-adaptation of both the external magnetic field and the drive current.

关键词： Brain-computer interface Biomagnetic detection gmi effect Working point self-adaptation Dual-loop control Magnetic gradiometer Differential noise reduction

Influence of the distance between two voltage contacts on giant magneto-impedance of Co-based amorphous wires

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Chinese Physics B 2010年第7期19卷 541-544页

作者：张树玲邢大伟孙剑飞 School of Materials Science and Engineering Harbin Institute of Technology

The Co75Fe4.2Si8B12Nb0.8 amorphous wires of 30μm in diameter are produced by melt extraction and annealing at 450℃ for 20 min in vacuum with a longitudinal or transverse field of 40 kA/m. Distances between the two voltage contacts of 6, 5, 4 and 2 mm are obtained by moving the two voltage contacts towards the centre of the sample at the same time. Results indicate that magneto-impedance response is dependent on the distance significantly. As distance decreases from 6 to 2 mm, AZ/Z reduces from 609% to 95% and giant magneto-impedance （gmi） profiles change from two-peak to single-peak. Besides, field sensitivity improves from 0.47%/（A/m） to 0.76%/（A/m） when the single-peak gmi just appears. It is therefore concluded that actual measurements can be made comparable only by taking into account the influence of distance between two voltage contacts for a magneto-impedance measurement.

关键词： gmi effect amorphous wire magnetic field anneal domain structure

Magnetic properties and giant magneto-impedance effect study of Fe-based nanocry-stalline powder

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Chinese Science Bulletin 2002年第2期47卷 102-104页

作者： ZHAO Zhenjie F.Bendjaballah JIANG Keyu RUAN Jianzhong YANG Xielong YANG Deping Department of Physics Key Laboratory for Optical and Magnetic Resonance SpectroscopyEast China Normal UniversityShanghai 200062China Department of Physics College of the Holy CrossWorcesterMassachusetts 01610USA

The macroscopic and microscopic magnetic properties for amorphous and nanocrystalline Fe73.5Cu1Nb3-Si13.5B9 powder have been investigated and their giant mag-neto-impedance (gmi) effect is reported for the first time. The experimental results show that powder sample annealed at 510℃ possesses the optimum soft magnetic properties. However, the maximum longitudinally driven gmi (LDgmi) ratio (about 52%) is found in the sample annealed at 600℃. This means that the LDgmi ratio depends on not only their magnetic properties but also their electric properties.

关键词： nanocrystalline gmi effect Mossbauer spectroscopy

Magnetization and giant magneto-impedance effect of Co-richmicrowires under different driven current

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Magnetization and giant magneto-impedance effect of Co-richm...