内应力对玻璃包覆钴基非晶丝巨磁阻抗的影响

通过测量玻璃包覆钴基非晶丝、去除玻璃包覆层非晶丝和经直流焦耳热退火后玻璃包覆非晶丝的磁阻抗值,研究了玻璃包覆层和直流退火对玻璃包覆钴基非晶丝内应力及巨磁阻抗效应的影响。结果表明:通过处理,玻璃包覆非晶丝的GMI最大值更容易在弱磁场出现;随着淬火残余内应力的改变,导致样品壳内畴的体积增加,引起应力感生横向各向异性,从而增强GMI效应;其中经90mA直流退火的样品GMI峰值最大可达144%。     

软磁非晶丝巨磁阻抗效应传感器研究进展与应用

基于软磁非晶丝巨磁阻抗效应(GMI)的传感器是近年来磁传感器领域的研究热点之一.非晶丝具有良好的软磁特性:如低电阻率、高磁导率、高饱和磁感应强度、低矫顽力、低损耗以及特殊的磁畴结构等,利用其GMI效应制成磁传感器,其突出优点是微型化、高灵敏度、快速响应、高温度稳定性和低功耗.本文讨论了软磁非晶丝巨磁阻抗效应的机理,叙述了非晶丝GMI传感器的研究进展,着重对敏感材料性能及制备、GMI器件结构形式、传感电路等作了介绍,并指出了GMI目前存在的问题及将来的发展趋势.最后对GMI的应用作了展望.     

基于巨磁阻抗效应的微磁传感器设计与实现

介绍了非晶带产生巨磁阻抗(GMI)效应的机理,对Co基非晶带进行了磁场后退火处理,磁阻抗比得到显著提高,为179%.在此基础上设计了一种基于GMI效应的磁传感器电路,详述了各个环节的电路设计.通过优化传感器电路相关的工作参数,改善了传感器输出性能并给出了典型结果.在常温下,非晶带激励电流频率为10 MHz时得到了非晶带...     

CoFe涂层对非晶薄带GMI效应的影响

上制备不同厚度的CoFe薄膜层,观察其巨磁阻抗(GMI)效应在120 kHz~3 MHz频率范围内随外加磁场的变化。实验结果显示,在Co基非晶薄带上涂覆CoFe薄膜,可提高薄带的GMI效应。研究发现,当趋肤效应显著时材料表面粗糙度对GMI效应有较大影响。通过在Co基非晶薄带表面镀膜的方式降低样品表面粗糙度,减小表面退磁场的影响,并闭合样品磁通回路,从而提高样品GMI效应。     

基于CoFeNbSiB非晶丝巨磁阻抗效应的新型磁传感器

本文利用CoFeNbSiB非晶丝的巨磁阻抗(GMI)效应制作了一种新型微磁场传感器.该传感器尺寸小,灵敏度高,反应速度快,且不需要预热.文章中具体介绍了非晶丝的特性、传感器的硬件及软件设计.     

激励电流对CoFeSiB非晶带GMI效应的影响

利用脉冲电流对Co基非晶带进行退火处理,研究了激励电流频率和幅值对非晶带巨磁阻抗(GMI)效应的影响。结果表明:该非晶带的特征频率为1.4MHz,磁场灵敏度Q在约1MHz下达到最大值1.46%/(A·m–1)。激励电流幅值增加,可以提高GMI变化率的最大值(ZGMI)max,磁场灵敏度却在激励电流幅值为7mA左右时达到最大值2.13%/(A·m–1)。     

纳米晶FeCuNbSiB带材巨磁阻抗效应研究

采用微机电系统(MEMS)技术,在玻璃基片上制备了单层结构500℃退火的FeCuNbSiB带材样品。在l～40MHz下,研究了带材的巨磁阻抗(GMI)效应随外加磁场强度以及交流电流频率的变化关系。结果表明:纵向、横向巨磁阻抗效应变化率(GMI值)在5MHz、1.2kA/m和5MHz、8kA/m时,分别达到最大值15.6%和10.6%。     

退火条件对FeSiCoB薄膜应力阻抗效应的影响

为了提高FeCoSiB薄膜和FeCoSiB/Cu/FeCoSiB多层膜的磁弹性能,利用磁控溅射方法在玻璃基片上沉积制备薄膜样品,并在真空中退火。测试了不同温度退火后,薄膜样品的应力阻抗效应。结果表明,退火处理条件对薄膜的应力阻抗效应有较大的影响。在6.4kA·m–1磁场下,薄膜经300℃、40min退火处理后,单层FeCoSiB和多层FeCoSiB/Cu/FeCoSiB的应力阻抗效应分别为1.86%和8.30%。     

巨磁阻抗传感器应用研究最新进展

利用零磁致伸缩非晶丝的巨磁阻抗(GMI)效应,可制得新一类灵敏度高、响应快、功耗低、体积小的微型磁电式传感器。介绍了目前几种基于巨磁阻抗效应的传感器,包括磁场传感器、扭矩传感器、汽车交通监测系统和生物传感器等的工作原理和特性。     

基于PXI和LabVIEW的巨磁阻抗测量系统

Co基非晶和Fe基纳米微晶材料中观察到巨磁阻抗效应(GMI),受国内外专家的广泛关注.为了对该效应的应用和开发作进一步研究,我们自行设计和制作了一套基于PXI和LabVIEW的巨磁阻抗测量系统.通过LabVIEW平台控制交流信号的产生和采集,由亥姆霍兹线圈提供外磁场.测试结果表明,该系统能够满足各类材料测定巨磁阻抗的要求,具有较好的重复性和较高的精度.     

FeCuNbCrSiB薄膜的制备及其巨磁阻抗效应研究

采用磁控溅射方法,在玻璃基片上制备了非晶的Fe73.5Cu1Nb3Cr0.5Si13B9薄膜及三明治结构M/C/M(M为Fe73.5Cu1Nb3Cr0.5Si13B9;C为Cu)的多层膜。在频率(1~40)MHz下,研究了薄膜材料的巨磁阻抗(GMI)效应随外加磁场的变化关系。结果表明:单层膜的GMI效应较小,只有4.4%;而三明治结构多层膜的GMI效应,比单层膜有较大幅度的提高,在5MHz、120Oe下,纵向和横向GMI效应分别达–17.4%和–20.7%。薄膜材料的纵向GMI效应随外加磁场变化呈现先增后减,而横向GMI效应随外加磁场的增加而单调递减,其变化规律与薄膜的易轴取向有很大关系。     

曲折形三层等宽FeCuNbSiB/Cu/FeCuNbSiB多层膜巨磁阻抗效应研究

采用磁控溅射方法,在玻璃基片上制备了曲折形三层等宽FeCuNbSiB/Cu/FeCuNbSiB多层膜。在1~40MHz下,研究了多层膜材料的巨磁阻抗(GMI)效应随外加磁场的变化关系。结果表明:在频率为5MHz、磁场强度为12kA/m下,横向和纵向GMI效应分别达–23.5%和–16.8%。薄膜材料的纵向、横向GMI效应随外加磁场变化呈现先增后降,而纵向表现尤为明显。     

Design of the Magnetic Properties of Fe‐Rich,Glass‐Coated Microwires for Technical Applications

The magnetic anisotropy of Fe‐rich, thin, amorphous wires is tailored by stress annealing (SA). In particular, the effect of conventional annealing (CA) and SA on the magnetic properties of Fe₇₄B₁₃Si₁₁C₂ glass‐coated microwires is studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain SA conditions (annealing temperature, T_ann > 300 °C; applied stress, σ > 400 MPa), a transverse magnetic anisotropy is induced: a rectangular hysteresis loop transforms into an inclined one at magnetic‐anisotropy fields above 1000 A m^–1. Under tensile stress, the rectangular hysteresis loop of microwires annealed using SA is recovered. Samples subjected to SA show noticeable magnetoimpedance and stress‐impedance effects, despite their large magnetostriction. The samples obtained exhibit a high stress sensitivity of their giant magnetoimpedance (GMI) effect and hysteretic properties, allowing the use of the obtained samples in magnetoelastic sensors, and for designing stress‐sensitive, tunable composite materials. By varying the time and temperature of such SA, we are able to tailor both the magnetic properties and the GMI of Fe‐rich microwires.     

CoFeSiB/Cu/CoFeSiB多层膜的巨磁阻抗效应研究

利用射频磁控溅射技术及微细加工技术制备了三明治结构的CoFeSiB/Cu/CoFeSiB多层膜,在频率l～40MHz下研究了多层膜的纵向和横向巨磁阻抗效应,结果表明曲折状三明治结构多层膜的巨磁阻抗效应比单层膜有较大的提高。在交流电流频率5MHz,外加直流磁场100Oe下巨磁阻抗变化率达17.3%。     

用于高灵敏微磁传感器的LMO膜制备与分析

采用溶胶凝胶法制备了LaMnOx(LMO)薄膜,系统研究了不同烧结温度、纵向直流磁场后退火和生长膜层数对LMO薄膜的巨磁阻抗效应的影响。结果表明,烧结温度、膜的层数以及纵向磁场后退火处理均有效提高了LMO的巨磁阻抗比,其中纵向直流磁场后退火处理提高薄膜阻抗比效果最显著,经过10Oe、400℃恒温1h磁场后退火处理后,在频率5MHz、100Oe外磁场下其磁阻抗比达15.8%,相比未后处理样品磁阻抗比提高了一倍,其对应的磁场灵敏度为0.16%/Oe。同时,实验发现磁场后退火不仅影响薄膜的巨磁阻抗比,也会改变阻抗比极大值所对应的激励频率,这一现象目前仍在探究中。     

Tuning of Magnetic Properties and GMI Effect of Co-Based Amorphous Microwires by Annealing

We studied the effect of annealing on the giant magnetoimpedance (GMI) effect, magnetic domain wall dynamics, and magnetic properties of amorphous iron (Fe) and cobalt (Co)-based microwires prepared by the Taylor–Ulitovsky technique. We observed that the properties can be tailored by controlling the magnetoelastic anisotropy of CoFeBSiC microwires during wire formation and also controlling the magnetic anisotropy by further heat treatment. A high GMI effect has been observed in the as-prepared Co-based microwires. High domain wall velocity and rectangular hysteresis loops have been observed in additionally heat-treated microwires. We observed increasing of the wall velocity under stress in some annealed samples. We demonstrated that, for certain annealing conditions, we can observe coexistence of the GMI effect and magnetic domain wall propagation in the same sample.     

Noise sources in miniature fluxgate sensors. Part II: the case of sensors with Fe77.5Si7.5B15 amorphous wire cores

As a continuation of Part I this paper is devoted to fluxgate sensors that employ Fe_77.5Si_7.5B₁₅ amorphous wires as magnetic cores, with attention being paid to fluxgate miniaturization. Two types of fluxgate sensors have been constructed. The first type is based on the high axial anisotropy exhibited by amorphous wires and employs two coils, an excitation and a receiving one. The second type employs the large Matteucci effect, owed to helical anisotropy induced into such wires either by mounting under torsion or by torsion annealing. The latter fluxgate type employs one single excitation coil. The exploitation of the Matteucci effect indicates that it may lead to the construction of miniature fluxgate sensors. The voltage-output of a series of such sensors has been sampled and processed. The repeatability of the flux-reversal process in the presence of helical or axial anisotropy is quantitative and qualitative investigated to allow for understanding the nature of noise. The existence of noise-sources that have been modeled in Part I is investigated and their power spectral density is estimated, from the experimental results. The influence of several manufacturing parameters in the noise at the output of fluxgates sensors is experimentally verified. Such parameters are the dimensions of the core, the presence and thickness of the glass-cover in glass-covered wires, the level of applied stress and torsion, working temperature level, and the characteristics of the excitation waveform. An irregular behavior at the hysteresis loop of fluxgates that employ the Matteucci effect is observed, which could be understood as a kind of perming effect. Measurements of the repeatability and hysteresis errors, of the sensors transfer function (output-voltage vs input-field), are presented, along with measurements of the cross-field sensitivity. The latter errors do not count as noise, but may limit the performance of fluxgates significantly, especially when miniaturization is attempted. Finally some design rules and manufacturing hints are proposed for fluxgate-magnetometer noise reduction.