Giant Magneto-Impedance Effect in Fe_(96-x)B_4 (x=7 or 10) Nanocrystalline Ribbons

The total ribbon voltage of as-quenched and annealed Fe96-xZr_xB_4 (x=7 or 10) ribbons has been measured as a function of applied dc field and drive current frequency. The experimental results show that both samples exist the optimum annealing temperature and optimum frequency at which the relative change in ribbon voltage is strongest, and the sensitivity of the magnetic response of the annealed Fe_89Zr_7B_4 ribbon is two order of magnitude larger than that of the annealed Fe_86Zr_10 B4 ribbon. The effect of magnetic properties and structural characteristics on giant magneto-impedance was discussed.

GIANT MAGNETO-IMPEDANCE OF PATTERNED FeSiB/Cu/FeSiB TRI-LAYER FILMS

Sensitive magnetic field sensor with good performances can be fabricated utilizing the giant magneto-impedance (GMI) effect of soft magnetic multi-layer thin films. The transverse and longitudinal GMI effect in patterned FeSiB/Cu/FeSiB tri-layer films with the change of external magnetic field and frequency were studied at the same time. The change of the impedance of the films with the external magnetic fieldand frequency was shown. Comparing the longitudinal and transverse effect, the transverse effect has a larger linear range from zero magnetic field to a quite large magnetic field at all frequencies, and the change still were not saturated until the external magnetic field reached 1.2×104A/m, which illustrated that the films can be utilized to detect larger magnetic fields than now presented GMI sensors.

Giant magneto-impedance effects in nanocrystalline soft magnetic alloy ribbons

SINCE the discovery of the giant magneto-impedance (GMI) effects in amorphous wire (or rib-bon) of CoFeSiB and nanocrystalline wire (or film) of FeCuNbSiB, it has attracted greatattention due to its promising potential applications in industry. Amorphous (and nanocrys-talline) soft magnetic alloys have very large magnetic permeability, when an ac driving currentand an external magnetic field (EMF) are applied, the EMF will damp the magnetic fluxchange caused by the ac driving current, thus the magnetic permeability will decrease; as a re-

Improvement of giant magneto impedance of Co-rich melt extraction wires by stress-current annealing

In order to improve the giant magneto impedance （GMI） of Co-rich wires for high sensitive sensor applications, Co6sFe4.sSilsBlz5 wires were prepared by melt an extraction technique and subjected to Joule stress-current anneal treatments with different tensile slresses applied. And then their GMI response was investigated at a frequency range from 0.1 to 13 MHz. It was found through the comparison of results that the GMI effect of these wires had been improved through stress-current anneal treatments, because the tensile stress applied on these Co-rich wires introduced magnetoelastic energy and increased anisotropy, which improved the circular permeability and GMI effect. Their impedance ratio AZ/Z increased from 244% to 480.9% at 7 MHz and the field sensitivity increased to 0.83%/（A/m） at 5 MHz, when a tensile stress of 244 MPa was applied at an anneal current of 100 mA for 10 min. It was therefore concluded that these annealed wires were suitable for high sensitive sensor applications.

Three-dimension micro magnetic detector based on GMI effect

The giant magneto-impedance（GMI）effect of amorphous wire was analyzed theoretically.The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680kHz and18 mV.A pulse generator was designed to provide high frequency pulse to a magnetic impedance（MI）element.The induced voltage on the pickup coil wound on the amorphous wire was sampled and held with a detect circuit using analog switch.A stable magnetic sensor was constructed.A three-dimension micro magnetic field detector was designed with a central controller MSP430F449.High stability and sensitivity were obtained in the MI sensor with the detect circuit.Experiment results showed that the resolution of the detector was 1nT in the full scale of±2 Oe and the detector worked stably from the room temperature to about 80℃.A small ferromagnetic target was detected by the three-dimension detector in laboratory environment without magnetic shielding.The target moving direction was ascertained with the wave shape of axis parallel in that direction.

Magneto-impedance effect in soft Fe-based nanocrystalline alloys

IN recent years, giant magneto-resistance (GMR) effects have been observed in some binary composite systems such as multi-layered and granular films of Fe, Co, Ni and Cr, Ag, Cu and attracted considerable interest due to their potential applications in magnetic recording heads and field sensors. However, a notable GMR effect in these films always requires a strong external magnetic field at low temperature. More recently, Mohri et al. have discovered

国外巨磁阻抗传感器检测电路技术的发展动态

基于非晶态合金材料巨磁阻抗(GMI)效应和非对称巨磁阻抗(AGMI)效应磁传感器是近20年来磁传感器技术领域的研究热点之一。一些国外学者认为非晶态合金材料适合于制作能同时满足分辨力高、响应速度快、功耗低等要求的微磁传感器。然而,迄今为止,国外研发的绝大多数高分辨力GMI磁传感器仍停留在原理样机阶段,其主要技术指标甚至低于商品化各向异性磁阻(AMR)和巨磁电阻(GMR)磁传感器。简要叙述了非晶态合金材料的GMI效应和退火处理对GMI效应的影响,重点介绍了国外研发的各种不同类型的基于非晶丝(带)的GMI磁探头、模拟信号检测电路及其参考性能指标,并探讨了研发高灵敏度GMI磁传感器的关键技术。

基于非晶合金非对称巨磁阻抗效应的磁传感器设计

以CoFeNiSiB非晶合金薄带为敏感材料,测试分析了其软磁性能,经空气中磁场退火热处理,获得了较好的非对称巨磁阻抗效应(AGMI)。以磁场退火处理后的非晶合金薄带为敏感元件,设计了AGMI磁传感器,并对其性能进行了开环和闭环测试。测试结果表明,开环条件下该传感器表现出较高的灵敏度;闭环条件下则表现出更好的线性度和更宽的测量范围。该传感器可实现对地磁场的检测,在地磁导航领域中具有较好的应用前景。

带材非对称巨磁阻抗效应的建模及数值计算

非对称巨磁阻抗效应具有高灵敏度的磁场响应.对于具有内部非晶软磁层和表面结晶层的带材,其非对称巨磁阻抗效应的传感建模是个复杂问题.文中针对这一问题,采用有效偏置场描述表层和内层之间的耦合作用,通过求解Landau-Lifshitz动力学方程和线性Maxwell方程得到器件的对角和非对角电压,并计算结晶层厚度变化时的磁场特性正反向工作区间和灵敏度.计算结果与实验基本相符,表明所建模型是可靠有效的.

正交激励与直流偏置的钴基非晶带弱磁传感器

通过纵横向正交激励与直流偏置的方式使脉冲电流退火钴基非晶带产生非对称巨磁阻抗（AGMI）效应,与仅使用横向激励方式相比,提高了单边GMI效应,包括：线性量程、阻抗磁灵敏度和最大阻抗变化率。在研究正交激励与直流偏置方式下非晶带特性的基础上,设计了钴基非晶带AGMI效应弱磁传感器并对传感器进行试验标定及数据分析,所得传感器性能指标：量程为-1.0~1.0 Oe,灵敏度为1.670 4 V/Oe,线性度为1.78%FS。