FeZrBCu射频溅射薄膜磁导率和巨磁阻抗效应的研究

采用射频溅射法在单晶硅衬底上制备了（Fe0.88Zr0.07B0.05）97Cu3薄膜样品。X射线衍射结果表明，未经任何后期处理的沉积态薄膜为非晶态结构。在5kHz～13MHz频率范围内，着重研究了沉积态样品的有效磁导率和巨磁阻抗（GMI）效应的变化特性。研究结果表明，样品具有极好的软磁性能和GMI效应，其矫顽力仅为58A／m，饱和磁化强度约为1．15×106A／m，在13MHz的频率下最大巨磁阻抗比达到17％。并发现有效磁导率比随外磁场的变化，在各向异性场仇。0．4kA／m处出现了峰值，GMI效应也在此磁场的位置处出现峰值。这表明GMI效应与磁场诱导的有效磁导率的变化紧密关联。     

熔体抽拉非晶微丝长度对巨磁阻抗的影响

研究了不同频率下非晶丝长度对巨磁阻抗(GMI)的影响规律和机制。低频下(<1MHz),由于边界效应对有效磁场的影响使得GMI效应随非晶丝长度减小而逐渐减小,1MHz时,随样品长度由20mm减小到4mm,其最大阻抗变化率ΔZ/Z由8.07%减小到1.03%;频率升高,由于趋肤效应和磁化机制的改变,而电阻随长度减小而减小利于获得大的环向磁导率,边界效应和电阻降低的共同影响下,存在一个最佳长度时,环向磁导率变化剧烈,GMI效应最强,结果表明直径34μm的熔体抽拉Co基非晶丝长度为7mm左右时,GMI效应最敏感,8MHz时最大ΔZ/Z达到86.1%。这一结果将为不同频率下MI传感器制备时样品长度选择提供参考。     

FeCuNbSiB多层膜的磁化特性与巨磁阻抗效应

用射频磁控溅射法制备了FeCuNbSiB多层膜，制备态样品的GMI效应在驱动电流频率为12MHz时达到最大，为44．3％。利用复数磁导率和等效电路讨论了该多层膜的磁化过程，及与GMI效应的关系。外加直流磁场抑制磁畴运动，在等效电路中与抵消并联电路相关。样品磁化的特征弛豫频率在12MHz左右，与出现最大磁阻抗变化的频率接近。     

非晶CoFeSiBMo合金微带磁性能及在MI磁敏感元件中的应用

采用单辊快淬法制备(Co0.942Fe0.058)71-x Si6.4B22.6Mox(x=0~5)非晶微带。合金微带的玻璃转化温度(Tg)随着Mo含量的增加由805K单调升高至832K;Mo含量为x=5时,过冷液相区ΔTx达最大值,表明添加Mo提高了该体系合金的非晶形成能力。饱和磁化强度(Ms)随Mo含量的增加而减小,但在Mo元素含量x=2时,矫顽力(Hc)值最小,有效磁导率(μe)最大。磁学性能测试结果显示,与常规热处理相比,磁场热处理对微带软磁性能改善更加明显。经过纵向磁场热处理,(Co0.942Fe0.058)69Si6.4B22.6Mo2非晶微带饱和磁化强度和有效磁导率分别达到80.99A·m2/kg和12 510,与制备态相比,分别增加40.15%和65.52%;而矫顽力为0.64A/m,减小48.39%。在驱动频率为43kHz时,以(Co0.942Fe0.058)69Si6.4B22.6Mo2为磁芯的MI磁敏感元件,对磁场灵敏度最大为136%/(A·m-1),对弱磁场响应灵敏。     

电流退火对CoFeSiB非晶丝和薄带的巨磁阻抗效应比较

采用熔融抽拉法和单辊急冷法分别制备了Co68.25Fe4.5Si12.25B15非晶丝和薄带。测量了制备态下两者的巨磁阻抗(GMI)效应,发现非晶丝的GMI比率高于薄带。研究了不同电流密度退火后非晶丝和薄带的GMI效应,结果发现ΔΖ/Ζ=[Z(H)-Z(H=0)]/Z(H=0)都明显上升,且非晶薄带数值更大;当电流密度等于0.96×107A/m2时,薄带的这一比率最大达到410%,磁场灵敏度达到5.1%/(A/m)。分析了出现上述现象的原因。     

GMI磁传感器的灵敏度和噪声研究现状

基于软磁非晶材料巨磁阻抗(giant magneto impedance,GMI)效应的传感器是近年来磁传感器领域的研究热点之一。GMI磁传感器具有微型化、高灵敏度、快速响应、高温度稳定性和低功耗等特点,在微弱磁场检测方面,具有广阔的应用前景。而高灵敏度与低噪音对GMI传感器尤为重要。然而,由于GMI效应及应用是近十几年刚刚发展起来的新领域,人们更多的关注GMI效应的基础理论研究,而GMI传感器相关理论研究相对较少。基于此,一方面介绍了GMI磁传感器灵敏度和噪声的国内外研究现状,同时介绍了GMI传感器的应用情况。     

不同退火过程对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(Fe88Zr7B5)0.96Cu0.04非晶软磁合金薄膜.研究了不同退火条件对其巨磁阻抗(GMI)效应的影响.该样品在自然退火和电流退火热处理后,纵向GMI比下降,并随退火电流的增加而增加,在电流为800mA时达到最大值17%,磁场灵敏度相对于未退火样品的4%(kA/m)-1有所提高,达到7%(kA/m)-1.(Fe88Zr7B5)0.96Cu0.04薄膜经不同温度下纵向磁场退火处理后,样品的纵向和横向GMI比均有所提高,在250℃获得最大的GMI比,13MHz时,最大纵向磁阻抗比达到17.5%,表现为单峰;横向磁阻抗比曲线变为双峰结构,在±0.4kA/m的磁场下,出现峰值为17.8%。     

FeCoB-Al2O3软磁颗粒膜磁特性研究

采用射频磁控倾斜共溅射制备了一系列的(Fe40Co40B20)1-x(Al2O3)x软磁颗粒膜。分别研究了基片转速及溅射气压对FeCoB–Al2O3薄膜微波磁特性影响。并通过改变FeCoB靶以及Al2O3靶的溅射功率进一步调控了软磁颗粒膜的磁特性和电阻率。研究结果表明在基片转速为60 r/min,溅射气压为0.2 Pa,FeCoB靶的溅射功率为250 W,Al2O3靶的溅射功率为100 W时,获得的FeCoB-Al2O3软磁颗粒膜具备了优良的软磁特性、微波磁特性和较高的电阻率。薄膜的饱和磁化强度为1.73 T,易轴难轴矫顽力均小于80 A/m,电阻率为126.75μΩ·cm,共振频率高达2.22 GHz,磁导率实部在2 GHz仍大于400。     

淬态FeNiCrSiB薄带的磁特性和纵向巨磁阻抗效应

采用单辊快淬法制备了(Fe50Ni50)77.5Cr0.5Si11B11合金薄带,测试了淬态薄带样品的微结构、静磁性能、磁导率和磁阻抗。研究结果表明,未经热处理的淬态(Fe50Ni50)77.5Cr0.5Si11B11合金薄带便具有良好的软磁性能和显著的巨磁阻抗效应,在7MHz频率下,纵向最大阻抗比达到31%。同时分析了几个典型频率下的纵向磁阻抗比、电阻比、电抗比和有效磁导率比随外磁场的变化行为,发现薄带样品的电抗比和有效磁导率比之间存在密切联系。由于内部结构的不均匀性,使得样品的横向各向异性场随驱动电流频率增大向高场方向移动。     

用Co部分置换Fe对Fe73.5Cu1Nb3Si13.5B9合金高频磁性的影响

研究了(Fe100-xCox)73 5Cu1Nb3Si13.5B9(x=0、50)纳米晶软磁合金的高频磁特性.结果表明,用Co部分置换Fe后,仍可形成纳米晶结构,并且可以显著提高合金的高频特性.与典型的Fe73.5Cu1Nb3Si13.5B9纳米晶软磁合金相比,其复数磁导率实部μ略有下降,但表征损耗的复数磁导率虚部μ"却大幅度降低,从而可显著提高软磁材料的截止使用频率fr及品质因数Q,本文初步探讨了在Fe73 5Cu1Nb3Si13.5B9合金基础上,用Co置换Fe而使高频特性得到改善的机理.     

软磁薄带巨磁阻抗效应的数值分析

利用磁畴壁移动模型以纳米晶软磁合金Ｆｅ７３．５Ｃｕ１Ｎｂ３Ｓｉ１３．５Ｂ９为例对软磁薄带中的巨磁阻抗效应进行了数值分析，结果发现不同的磁导率机制并不能显著发迹巨巨磁阻抗效的大小仅由磁导率对外加磁场的敏感性决定，从趋肤深度的角度讨论了巨磁阻抗效应的频率特性。     

三明治结构FeNi/Cu/FeNi多层膜巨磁阻抗效应研究

采用MEMS技术在玻璃基片上制备了三明治结构FeNi/Cu/FeNi多层膜,在1～40 MHz范围内研究了FeNi/Cu/FeNi多层膜中的巨磁阻抗效应特性.当磁场Ha施加在薄膜的长方向时,巨磁阻抗效应随磁场的增加而增加,在某一磁场下达到最大值,然后随磁场的增加而下降到负的巨磁阻抗效应.在频率为5MHz时,巨磁阻抗效应在磁场Ha=800 A/m时达到最大值26.6%.巨磁阻抗效应的最大值及负的巨磁阻抗效应与多层膜中磁各向异性轴的取向及发散有关.另外,当磁场施加在薄膜的短方向时,薄膜表现出负的巨磁阻抗效应,在频率5 MHz、磁场Ha=9600 A/m时,巨磁阻抗效应可达-15.6%.     

同轴电缆结构复合丝巨磁阻抗效应的研究

采用脉冲电沉积工艺在直径为200μm的铜丝表面沉积铁镍合金镀层,形成具有同轴电缆结构的巨磁阻抗复合丝材料。分别改变复合丝磁性外壳厚度与铜丝直径,研究复合丝结构对巨磁阻抗效应的影响。发现巨磁阻抗比值随磁性外壳厚度的增大及铜丝直径的增大而增大,特征频率则向低频端移动。本文还发现在外加直流磁场低于5．57kA／m时,驱动交流电幅值增大,巨磁阻抗效应增大;高于5．57kA／m时,驱动交流电幅值的大小几乎不再影响复合丝的巨磁阻抗效应。在驱动电流上叠加20mA以下的直流偏置对巨磁阻抗效应没有影响。     

Preparation and Properties of Amorphous NiFe/Cu/NiFe Thin Films

The amorphous of Permalloy on the copper subtract was studied using composite electroplating method. A portion of hydrogen brings the counteraction on the surface of cathode leading nickel-iron alloys to be anomalous in the process of co-depositing. The results of X-ray diffraction (XRD) show that the Ni-Fe alloys layer is amorphous. The Giant Magneto -Impedance (GMI) effect of Ni-Fe alloys was obtained under the optimal conditions, dependence on the soft magnetic property of Ni-Fe amorphous thin film. As a result, the ratios△ Z/Z of NiFe/Cu/NiFe amorphous thin film are 30% at 40 kHz which is in low frequency. Furthermore, the GMI value of NiFe/Cu/NiFe amorphous thin film with a sandwich structure is higher than that of single-layer ferromagnetic films of the same thickness.     

复合丝巨磁阻抗效应的研究

利用化学渡方法制备了芯层为铁磁层和芯层为导电层的两种复合丝,比较研究了它们的巨磁阻抗特性,结果发现芯层为铁磁层的复合丝在60MHz时取得最大值107%,而芯层为BeCu的复合丝在300kHz时就获得最大值108%.这是因为BeCu/绝缘层/NiCoP在低频时有较大的磁电阻效应,同时,由于芯层电阻较小,R与X在较低频就可比拟.磁阻抗比不仅取决于磁电阻比、磁感抗比,还与R和X的相对比值有关.要想获得显著的磁阻抗效应,要求材料不仅具有良好的软磁特性,而且电流通过部分还具有电阻率小的特点.     

高磷含量CoP-Cu复合丝巨磁阻抗效应的频谱特性

控制电化学工艺条件在直径为200μm的铜丝表面合成CoP磁性镀层成功地制备出高磷含量CoP—Cu复合丝巨磁阻抗效应材料。当磷含量为20%（原子分数）时,复合丝巨磁阻抗效应非常显著,达80%以上。本文详细研究了复合丝材料的频谱及巨磁阻抗效应频谱,指出复合丝巨磁阻抗具有较低的特征频率及较宽的频率使用范围与此新型结构有关,本文还发现,随频率的增加,最大负巨磁阻抗比对应的外加直流磁场也在增加,并且在高频与低频时,巨磁阻抗效应随磁场的响应曲线明显不同。     

FeSiB薄膜的巨磁阻抗和应力阻抗效应研究

软磁材料中存在巨磁阻抗 (giantmagneto impedance ,GMI)效应以及与之相同来源的应力阻抗 (stress impedance ,SI)效应 ,利用这两种效应可以制成具有高灵敏度的微型化的磁场和应力 应变传感器。本文基于传感器的实际应用 ,对图形化的、较大磁致伸缩的FeSiB单层和多层薄膜的巨磁阻抗和应力阻抗效应中频率和退火的影响进行了研究。结果表明 ,对于两种效应 ,经过退火处理的单层和多层膜均可在较低的频率下得到较高的灵敏度 ,而多层膜中的应力阻抗效应将为新型高灵敏传感器的设计和研制开辟一条崭新的途径     

Simulation of Giant Magnetic Impedance (GMI) Effect in Co-based Amorphous Ribbons with Demagnetizing Field

Considering the role of demagnetizing field, based on linear Maxwell’s equations and the Landau-Lifshitz equation, the expressions of permeability and impedance were obtained using the improved theoretical model in this article. A numerical simulation was conducted using Matlab, and the results of calculations were well matched with the experimental results, indicating the importance of the demagnetizing field and that it should not be ignored. Utilizing the equivalence relation between the shape of the samples and the demagnetization factor which determined the value of the demagnetizing field, the influence of the aspect ratio of the samples on giant magnetic impedance (GMI) effect was researched. The calculations showed that the most significant GMI effect was obtained when the aspect ratio of samples was about 44. In addition, the optimal frequency to obtain the most significant GMI effect of the given sample was calculated. These researches may provide theoretical guidance for the development and use of a GMI sensor.     

High frequency magnetic properties and intergranule interaction of nano-granular films with high resistivity and high permeability

In order to get magnetic films with high permeability and high resistivity for applications in high frequency devices, (Fe65Co35)x(SiO2)1-x nano-granular films with low metal volume fraction were fabricated by radio frequency magnetron sputtering, and excellent soft magnetic properties have been acquired by annealing the sample with x = 0.38 at 260 degrees C in a magnetic field. The real part micro' of complex permeability is larger than 100 when frequency f is lower than 0.7 GHz, and the ferromagnetic resonance frequency f(r) is as high as 1.8 GHz. More interestedly, the resistivity of this sample reaches 13.4 momega x cm, 4 orders higher than that of pure FeCo alloy. Ferromagnetic resonance experiment and deltam-H curve study were employed to elucidate the mechanism of soft magnetic properties. The results reveal that the intergranule exchange coupling plays an important role in realizing good soft magnetic properties for metal-insulator granular films.     

Thermal annealing dependence of high-frequency magnetoimpedance in amorphous and nanocrystalline FeSiBCuNb ribbons

The magnetoimpedance (MI) effect in Fe73.5Si13.5B9Nb3Cu1 melt-spun amorphous ribbons has been studied in the frequency range (1-500 MHz). Isothermal heating treatments in a furnace have been employed to nanocrystallize the ribbons (1 h at 565 degrees C in a vacuum of 10(-3) mbar), while other samples were annealed at lower temperatures (400 and 475 degrees C during 1 h), in order to evaluate the influence of the annealing temperature on the MI effect. The high-frequency impedance was measured using a technique based on the reflection coefficient measurements of a specific transmission line by using a network analyzer. Frequency dependence of the MI ratio, DeltaZ/Z, and both resistive, DeltaR/R, and reactive, DeltaX/X, components of magnetoimpedance were measured in the amorphous and annealed states, at different temperatures. A maximum value of the MI ratio of about 50% at a driving frequency of 18 MHz is obtained in the nanocrystalline (annealed at 565 degrees C) ribbon. Maxima for DeltaR/R of about 81% at 85 MHz and DeltaX/X around 140% at 5 MHz were also achieved. It is revealed that the microstructural evolution in the nanocrystalline sample leads to a magnetic softening, an optimum domain structure and a permeability which is sensitive to frequency and applied magnetic field, generating a large MI response.