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.     

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。     

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%。     

Temperature-Dependent Giant Magnetoimpedance Effect in Amorphous Soft Magnets

Giant magnetoimpedance (GMI)-based devices offer potential as next-generation low-cost, flexible, ultrasensitive sensors. They can be used in applications that include current sensors, field sensors, stress sensors, and others. Challenging applications involve operation at high temperatures, and therefore studies of GMI temperature dependence and performance of soft magnetic materials are needed. We present a high-temperature GMI study on an amorphous soft magnetic microwire from room temperature to 560°C. The GMI ratio was observed to be nearly constant at ～86% at low temperatures and to decrease rapidly at ～290°C, finally reaching a near-zero value at 500°C. The rapid drop in GMI ratio at 290°C is associated with a reduction in the long-range ferromagnetic order as measured by the spontaneous magnetization (M) at the Curie temperature (T _c). We also correlated the impedance with the magnetic properties of the material. From room temperature to 290°C, the impedance was found to be proportional to the square root of the magnetization to magnetic anisotropy ratio. Lastly, M(T) has been fit using a Handrich–Kobe model, which describes the system with a modified Brillouin function and an asymmetrical distribution of exchange interactions. We infer that the structural fluctuations of the amorphous phase result in a relatively small asymmetry in the fluctuation parameters.     

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...     

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。     

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.     

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。     

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.     

FeCuNbCrSiB/Cu/FeCuNbCrSiB薄膜各层宽度对其巨磁阻抗效应的影响

采用射频磁控溅射方法，利用微细加工工艺制备了不同薄膜宽度的三明治结构FeCuNbCrSiB／Cu／FeCuNbCrSiB多层膜，在频率1～40MHz下研究了薄膜宽度对多层膜的纵向和横向巨磁阻抗效应的影响。结果表明，三明治结构多层膜的巨磁阻抗效应随薄膜宽度的变化具有显著的影响，当FeCuNbCrSiB层、Cu层宽度分别取1．6rflrn、O．8rflrn时，GMI％达到最大值一21．22645％。     

张应力退火对玻璃包覆钴基非晶丝GMI影响

采用张应力–焦耳热方式对玻璃包覆钴基非晶丝进行退火,测量其退火后的磁滞回线和磁阻抗值,研究张应力退火对玻璃包覆钴基非晶丝静磁性能和巨磁阻抗(GMI)效应的影响。结果表明:通过处理,其各向异性场降低,其中经140MPa张应力退火的样品GMI峰值最大可达80%,所对应的磁场强度降至60A/m。随着玻璃包覆钴基非晶丝内应力的改变,导致样品壳内畴的体积增加,引起应力感生横向各向异性,从而影响GMI效应。     

Multilayer Microwires: Tailoring Magnetic Behavior by Sputtering and Electroplating

A novel technique for preparing multilayer microwires with controlled magnetic behavior has been developed. This technique involves combining sputtering and electroplating procedures to deposit (magnetic or non‐magnetic) metallic nano‐ and microlayers onto glass‐coated amorphous magnetic microwires. A suitable choice of magnetostrictive amorphous metallic nucleus, together with the specific stresses induced by the deposited layers, allows the tailoring of specific magnetic behavior. In this way, the preparation of multilayer microwires characterized either by square‐shaped hysteretic loops (typical of magnetically bistable microwires with longitudinal easy axes), or by nearly non‐hysteretic loops (for those microwires with a circumferential magnetization easy axes), can be achieved.     

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%。     

曲折型三明治结构FeNi/Cu/FeNi多层膜巨磁阻抗效应研究

采用微机电系统(MEMS)技术在玻璃基片上制备了曲折型三明治结构FeNi/Cu/FeNi多层膜,在电流频率1～40 MHz范围内研究了FeNi/Cu/FeNi多层膜的巨磁阻抗(GMI)效应,并分别通过改变FeNi薄膜的宽度、厚度和Cu薄膜的宽度,研究了尺寸对巨磁阻抗效应的影响,当磁场Ha施加在薄膜的纵轴时,巨磁阻抗变化...     

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.     

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%。     

电子束诱导沉积钴微米线及其铁磁性

通过电子束诱导沉积的方法制备了钴(Co)微米线,并利用扫描电子显微镜(SEM)、原子力/磁力显微镜(AFM/MFM)以及物性测量系统(PPMS)等手段对Co微米线的沉积尺寸、微结构、铁磁性和电学性质进行了测试和分析。研究结果表明:Co微米线轮廓清晰、均匀性好。在不同的沉积条件下,微米线的实际长度与设定长度基本一致;实际宽度数据呈类梯形分布,半高宽是设定值的2~10倍;实际厚度低于设定厚度的60%。沉积电流对Co微米线的铁磁特性有重要影响。当沉积电流大于0.5 nA时,样品呈现出良好的铁磁特性。另外,电学性能测试结果显示Co微米线呈现绝缘特性。成功制备了室温铁磁绝缘Co微米线,这将有助于深入开展微纳尺度的结构与器件的研究和应用。     

非晶带GMI效应闭环弱磁场传感器

利用脉冲电流退火处理后的Co66.3Fe3.7Si12B18非晶带作为敏感元件,研制出一种基于非晶带GMI效应的闭环磁场传感器。分析了传感器的工作原理,设计了传感器的信号处理以及负反馈电路,并对传感器性能进行了测试。闭环传感器在线性量程为±260A/m范围内,线性度提高为0.49%。传感器可应用于地球磁场、环境磁场等微弱磁场检测领域。     

玻璃包覆磁性合金微丝性能研究进展

综述了玻璃包覆磁性合金微丝复合材料的制备、磁性能及高频电磁性能的研究进展。分析了玻璃包覆磁性合金微丝的特点及成为研究热点的原因。归纳了不同磁致伸缩系数微丝的磁结构研究,尺寸、长度、热处理及含量等对玻璃包覆磁性合金微丝的磁性能及高频电磁性能的影响,展望了它在传感器、微波与吸波方面的应用前景。     

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)。