FeCuCrVSiB单层和多层膜的横向巨磁阻抗效应

用射频溅射法制备了Fe_71.5Cu₁Cr_2.5V₄Si₁₂B₉单层膜和结构为(F/S)₃/M/(F/S)₃的多层膜，在制备过程中加72kA/m的纵向磁场.研究表明在制备过程中加磁场明显改善了材料的软磁性能，降低了材料的矫顽力.将样品经不同温度退火热处理后，发现经230℃退火1.5h的单层膜和多层膜具有最佳的软磁性能和最大的磁阻抗效应，单层膜最大横向磁阻抗比为37.5%，多层膜最大横向磁阻抗比高达277%.通过比较单层和多层膜磁阻抗效应随频率和磁场的变化，发现多层膜具有较低的磁阻抗效应的临界频率和峰值特征频率，和较大的磁阻抗变化率，而且有较低的横向磁阻抗效应的饱和场. 关键词： 铁基合金 多层膜 巨磁阻抗效应     

FeCuCrVSiB多层膜巨磁阻抗效应的研究

研究了结构为 (FM/SiO₂)₃/Ag/(SiO₂/FM)₃ 多层膜的巨磁阻抗(GMI)效应（这里的F M≡FeCuCrVSiB）．多层膜采用射频溅射法沉积在单晶Si衬底上，沉积过程中，沿膜面长方 向施加约72kA/m的磁场，然后在不同的温度下对样品进行了退火处理．结果表明，该多层膜 样品即使在沉积态便具有相当好的软磁性能和GMI效应，在7MHz的频率下，最大纵向和横向 巨磁阻抗比分别为45%和44%．在230℃下经90min退火处理后的样品具有最佳的GMI效应，在85MHz的频率下，最大纵向和横向巨磁阻抗比分别达到251%和277%．与磁性层总厚度相同的FeCuCrVSiB/Ag/FeCuCrVSiB三层膜相比较，在这种多层结构中出现的GMI效应更强． 关键词： 多层膜 巨磁阻抗效应 趋肤效应 有效磁导率     

电流退火铁基薄带巨磁阻抗效应的影响

研究了电流退火工艺对铁基非晶合金Fe₈₄Zr₈Nb_3.5B_3.5Cu_{1〈/sub>薄带巨磁阻抗效应的影响.实验结果表明,该铁基合金的巨磁阻抗ΔZ/Z随退火电流的增加而增强,当电流为820mA时,ΔZ/Z达到最大值62％,阻抗变化灵敏度可达约0.23％（A/m)^-1.结合此合金在电流退火燧后电性能和软磁性能的演变,讨论了材料的巨磁阻抗效应借助趋肤效应与交流频率和外加纵向磁场的关系. 关键词：}     

Evolution of magnetic permeability and magneto-impedance effect in composite wires with insulator layer

CuBe/Insulator/NiCoP composite wire was prepared by electroless deposition on an insulated CuBe core with a diameter of 90 μm. The conversion relationship between the magneto-impedance and effective magnetic permeability of the composite wire was derived from an energy conversion model. The evolution of the magnetic permeability and the giant magneto-impedance (GMI) effect were investigated. The results show that a distinct GMI effect can be obtained at relatively low frequency. The largest GMI ratio is 240% at 600 kHz, and the maximal field sensitivity is 34%/Oe.     

Large GMI effect in Co-rich amorphous wire by tensile stress

Quality Co₆₈Fe_4.5Si₁₅B_12.5 amorphous wires are fabricated and their giant magneto impedance (GMI) effect are investigated at frequencies ranging from 0.1 to 20 MHz with or without tensile stress applied. Experimental results indicate that the GMI effect of these wires can be effectively improved by applying a small axial tensile stress. There is a pronounced increase from 1.3% to 47.3% in impedance ratio at 0.6 MHz when a stress of 103 MPa is applied. The GMI response is further increased to 261% by doing so at 15 MHz. The field sensitivity of these wires is optimized and it increases from 0.55 to 2.73%/(A/m) at 0.6 MHz and it is proved that the most sensitive field response is obtained by applying a tensile stress of 84.5 MPa below 1 MHz. With reference to the stress evolution of sensitivity at varying frequencies, the maximum field sensitivity shifts to a lower stress with increasing frequency. Quantitatively, a stress as small as 18.4 MPa is enough to yield a field sensitivity as high as 6.7%/(A/m) at 15 MHz. This demonstrates the possibility of achieving small stress (<100 MPa) induced large enhancement of GMI effect and field sensitivity at frequencies of several tens of MHz that are of much technical interest in sensor applications.     

Longitudinally driven giant magneto-impedance effect enhancement by magneto-mechanical resonance

Longitudinally driven giant magneto-impedance (GMI) effect in amorphous magnetostrictive Fe₂₄Co_11.82Ni_47.3Si_1.47B₁₅ ribbons was investigated. The experimental results showed that the magneto-mechanical resonance of the ribbons had significantly enhanced GMI effect. The strong magneto-mechanical coupling (MMC) interaction resulted in high MI ratio. Maximal GMI ratio of 1532% was obtained in the sample annealed at 340 °C under transverse magnetic field. The results are explained in terms of MMC and resonance of the magnetostrictive materials.     

Dependence of the driving current on the harmonic behavior of giant magneto-impedance voltage of Co-based amorphous wires

The frequency and the amplitude of the driving AC current dependence on the harmonic behavior of the giant magneto-impedance (GMI) voltage of Co-rich amorphous wire have been studied. Single-peak, two-peak and three-peak behavior in the GMI characteristics was studied with the change of amplitude and frequency of the AC current. GMI ratio was calculated from the first harmonic signals which were initially increased and then decreased monotonically with the increase of frequency (f) and the amplitude (I_AC) of the driving current. The response of the GMI voltage was found non-linear with the generation of higher harmonics at higher amplitude of the driving current. The second and third harmonic signals were also evaluated and their dependence on the driving current amplitude and frequency were presented in the paper. The experimental results were analyzed using single domain rotational model. The voltage harmonics were calculated through Fourier transform of the time derivative of the estimated circular magnetization of the sample.     

射频溅射功率对FeZrBCu软磁合金薄膜巨磁阻抗效应的影响

用射频溅射法制备了FeZrBCu软磁合金薄膜.研究了不同溅射功率对FeZrBCu薄膜软磁特性和巨磁阻抗效应的影响.用电子探针显微镜测量发现，当溅射功率为240W时，薄膜样品中Fe的原子含量为8732%，Cu的原子含量为29%.这种样品的矫顽力最小，为68A/m，饱和磁化强度约为111×105⁵A/m，软磁性能最佳，巨磁阻抗效应最大，溅态膜在 13MHz最大巨磁阻抗比纵向为17%，横向为11%.重点分析了阻抗的电阻、电感分量及横向有 效磁导率随频率的变化，得到在低频下主要是磁电感 关键词： 铁基合金 薄膜 巨磁阻抗效应     

Structural and Giant Magneto-impedance properties of Cr-incorporated Co-Fe-Si-B amorphous microwires

The investigation is focused on the effect of Cr incorporation for Co/Fe in (Co_0.5Fe_0.5)_78−xCr_xSi₈B₁₄ (x=0-12) amorphous microwires of 110 μm diameter prepared by in-water quenching technique. The rise in crystallization onset T_X1 with Cr addition revealed the elemental contribution against devitrification and a consequent thermal stability. Cr is unfavorable towards ferromagnetic ordering leading to a linear drop in Curie temperature T_ca with its rise in concentration. The presence of low Cr content upto Cr-4 at.% has been effective in drastically improving the Giant magneto-impedance (GMI) property. Cr content in the range of 4≤X≤10 has low magnetostriction and maximum field sensitivity in the as-quenched state. The GMI properties are further improved after annealing treatment. High content of Cr>10 is found to be deleterious towards GMI behavior and its consequent application as sensor material.     

Enhancement of giant magneto-impedance effect in Ni80Fe20/SiO2/Cu composite wires

Ni₈₀Fe₂₀/SiO₂/Cu composite wires of Cu core 60 μm in diameter and coated with layers of SiO₂ and Ni₈₀Fe₂₀ were prepared by RF magnetron sputtering. The influences of the insulator layer thickness, the measurement mode and the magnitude of the driving current on the giant magneto-impedance (GMI) effect were investigated. The results showed that there was an optimum thickness of the insulator layer and the driving current can influence the shape of the MI curve. Resonance enhancement of the GMI was found in the new measurement mode. The results are discussed by taking account of the electromagnetic interactions.     

TbDyFe薄膜对三明治膜巨磁阻抗效应的影响

将600℃退火后的超磁致伸缩材料(Tb0.27Dy_0.73)_0.3Fe_0.7薄膜作为Ni_80.2Fe_14.1Si_0.2Mn_0.4Mo_5.1三明治膜的基底，制备出四层膜.结果表明：附加的磁致伸缩并没有减小材料的巨磁阻抗(GMI)效应，而由于磁场下磁致伸缩材料的应力效应影响了三明治膜中的各向异性场，使三明治膜的GMI效应增大了4倍.再将制备态的四层膜在280℃下真空退火，退火态四层膜也增大了三明治膜的GMI效应，但可能由于磁致伸缩向磁性层中的扩散，其GMI效应相对于制备态四层膜则有所降低. 关键词： 巨磁阻抗(GMI)效应 三明治膜 TbDyFe薄膜 各向异性场     

Magneto-Impedance behavior of Co-Fe-Nb-Si-B-based ribbons

The giant magneto-impedance of melt spun Co_xFe_72−xNb₄Si₄B₂₀(x=10, 20, 36, 50) amorphous and nanostructured ribbons have been investigated. Alloys have been optimized at the driving current amplitude, frequency and found that amorphous ribbon of nominal composition of Co₃₆Fe₃₆Nb₄Si₄B₂₀ shown maximum GMI ratio of 13%. The behaviour of the driving current amplitude on the GMI behaviour was studied and the sample was optimized for driving current amplitude, I_ac=10 mA. The frequency dependence of the GMI behaviour was studied for the ribbon sample Co₃₆Fe₃₆Nb₄Si₄B₂₀ at frequency in the range of 100 kHz-1.2 MHz of the optimized driving current amplitude and it was found that the sample showed the maximum GMI behaviour at f=700 kHz. The optimized samples were Joule heated at the current density J=0-35 A/m² for a period of 1 min. The GMI ratio initially increased then progressively deteriorated with J, but after a certain range it shows up to 16% of improvement in the magneto-impedance value due the increase of nanocrystalline volume fraction. The asymmetry in the GMI profile was observed for the sample Joule heated at J=1-5 A/m² for 1 min.     

Cytotoxicity and GMI bio-sensor detection of maghemite nanoparticles internalized into cells

In this work we determine conditions to produce cell samples for imaging with detection of the modification of the magnetic field by maghemite (Fe₂O₃) nanoparticles acting as a high sensitivity magnetic bio-sensor based on the giant magneto-impedance (GMI) effect. Mat Ly Lu cells are grown for 24 h with various maghemite nanoparticles concentrations (from 0 to 6 mg/ml). The percentage of viable cells is determined by counting labeled cells with trypan blue under an optical microscope. The quantity of nanoparticles internalized into the cells is evaluated by X-ray fluorescence analysis and expressed in iron moles per cell. The GMI bio-sensor was tested with the various samples. We observed that the best sensitivity of the GMI bio-sensor was obtained at a frequency of 1 MHz. To confirm these results in the presence of cell samples, four measurement frequencies were pre-selected (from 1 to 100 MHz) and tested. Cell growth conditions compatible with an acceptable percentage of cell viability for various concentrations of nanoparticles were also determined. These experiments allow us to conclude that cell growth with 0.1 mg/ml of nanoparticles for 24 h shows modifications of the magnetic field detectable optimally at 1 MHz frequency.     

非晶CoFeNiNbSiB合金的巨磁阻抗效应

研究了非晶Co₇₀Fe_4.5Ni₄Nb₁Si_12.5B₈合金薄带的巨磁阻抗效应.实验表明,在一定频率范围内提高测试频率,磁阻抗效应有明显提高;适当温度的退火也有助于磁阻抗效应的提高.制备态非晶合金样品在频率为5MHz下达120%左右,经过退火处理的非晶样品5MHz下的效应可达400%左右. 关键词：     

Giant magneto-impedance and stress-impedance effects of microwire composites for sensing applications

Composites consisting of glass-coated amorphous microwire Co_68.59Fe_4.84Si_12.41B_14.16 and 913 E-glass prepregs were designed and fabricated. The influences of tensile stress, annealing and number of composite layers on the giant magneto-impedance (GMI) and giant stress-impedance (GSI) effects in these composites were investigated systematically. It was found that the application of tensile stress along the microwire axis or an increase in the number of composite layers reduced the GMI effect and increased the circular anisotropy field, while the annealing treatment had a reverse effect. The value of matrix-wire interfacial stress calculated via the GMI profiles coincided with the value of the applied effective tensile stress to yield similar GMI profiles. Enhancement of the GSI effect was achieved in the composites relative to their single microwire inclusion. These findings are important for the development of functional microwire-based composites for magnetic- and stress-sensing applications. They also open up a new route for probing the interfacial stress in fibre-reinforced polymer (FRP) composites.     

介观结构对纳米晶软磁合金巨磁阻抗效应影响的理论分析

根据用原子力显微镜对Fe基纳米晶Fe_73.5Cu₁Nb₃Si_13.5B₉合金薄带的介观结构和巨磁阻抗效应的实验研究结果，提出了纳米晶软磁合金巨磁阻抗效应受其介观结构影响的理论模型.该模型成功地解释了低频对纳米晶软磁合金巨磁阻抗效应的影响，反映了现有“三明治”理论的主要特征，并弥补了它的不足；同时指出了纳米晶粒电导率σ、磁导率μ对合金巨磁阻抗效应有影响. 关键词： 铁基纳米晶合金 介观结构 巨磁阻抗效应 介观模型     

Observations of magnetic coupling in Fe-based nanocrystalline alloy by high-temperature giant magneto-impedance effect

The giant magneto-impedance (GMI) effect for Fe_73.5Cu₁Nb₃Si_13.5B₉ nanocrystalline ribbons is investigated in the temperature range between room temperature and 873 K. The thermal dependence of GMI effect reveals the enhancement of Curie temperature of the amorphous matrix, reflecting the exchange coupling between the α-FeSi grains as well as the compositional changes of the amorphous matrix itself. However, the dipolar interaction between grains is suggested to be responsible for the non-zero GMI effect after the magnetic phase transition of the amorphous matrix.     

FeCuNbSiB单层膜和三明治膜的磁特性与巨磁阻抗效应

用射频溅射法制备了Fe_73.5Cu₁Nb₃Si_13.5B₉单层膜和 Cu或Ag作为中间层的三明治膜.溅态膜为非晶态结构.磁畴观察结果表明,单层膜在380℃退火后,呈现均匀磁化的纳米晶结构,该样品软磁特性最佳,其巨磁阻抗效应最大,在13MHz,最大磁阻抗比纵向为18％,横向为14％.溅态三明治膜具有较大的巨磁阻抗效应,在13MHz,Cu夹层三明治膜的最大磁阻抗比纵向为32％,横向为11％,Ag夹层三明治膜的最大磁阻抗比纵向为47％,横向为57％.Cu夹层三明治膜经250℃退火后,在低频下表现为巨磁电感效应,在100kHz,最大磁电感比为1733％. 关键词：     

Preparation of meander thin-film microsensor and investigation the influence of structural parameters on the giant magnetoimpedance effect

A novel GMI-based microsensor with symmetrical meander structure has been fabricated by MEMS technology and mutual perpendicularity between longitudinal external field and easy axis was established by electroplating process for reaching a higher GMI. The GMI effects of the 3 and 6 turns sample with different Cu line width has been investigated systematically. The longitudinal frequency dependence has been given and a new frequency characteristic was observed in this paper. The experimental results show the increasing of Cu line width in appropriate range and more turns can respectively lead to greater GMI effect, the positive GMI ratio peak in 6 turns sample is nearly 4.5 times over the 3 turns sample, the peak frequency is greatly increased with the increasing of turn number, and the GMI ratio in 3 and 6 turns sample both exhibits negative maximum value when H _L>50 Oe. In this work, the GMI ratio peak appears at f _AC=4.8 MHz in 6 turns sample with the Cu line width of 140 μm, almost reaches 183.7 % under H _L=17 Oe.     

铁基纳米晶合金的介观阻抗率及应用

提出了铁基纳米晶合金介观阻抗率的物理概念,用Maxwell方程组求得其计算公式ρ=-μ{A}/{t}/Δ×H,该式表明铁基纳米晶合金的介观阻抗率与材料内部的介观磁场强度H、介观磁矢势A和介观磁导率μ有关,磁矢势A是由介观结构引起的量子力学效应,是由合金的微观结构决定的.这个理论很好地解释了铁基纳米晶粉末、粉芯 关键词： Fe基纳米晶合金 介观阻抗率