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。     

制备态(Fe88Zr7B5)100-xCux非晶薄膜的磁特性和巨磁阻抗

采用射频溅射法在单晶Si衬底上制备了Fe88Zr7B5)100-xCux(x=0、1、2、3、4)非晶薄膜样品,对其软磁特性和巨磁阻抗(GMI)变化行为进行了测量和研究。测量结果显示,加入适量Cu元素(x=3)的制备态样品具有极好的软磁性能和GMI效应,此样品的矫顽力仅有56A/m,在13MHz的频率下,最大有效磁导率(μe)比和GMI比分别为42.5%和17.0%。研究发现,制备态样品的电阻R、电抗X和阻抗Z都随Cu含量的增加而下降。X=0、4两个样品的μe、R、X、Z对外加磁场响应极不敏感,只有软磁性能优异的x=3样品的μe、R、X、Z才显示出对外加磁场响应敏感,因而有显著的GMI效应。样品拥有高的磁导率、小的矫顽力和低的电阻率是获得大GMI效应的本质条件。     

焦耳-应力退火对Co基薄带巨磁阻抗的影响

采用焦耳-应力退火处理了Co_83.2Fe_5.2Si_8.8B_2.8非晶薄带,利用阻抗分析仪和磁光克尔效应显微镜分析了焦耳-应力退火前后Co基薄带的巨磁阻抗效应和磁畴结构。结果表明,经焦耳-应力退火后,薄带的GMI效应得到提高,24.5 MPa焦耳-应力退火后,0.4 MHz时,薄带的最大阻抗变化率达到47.6%,1 MHz时,其磁场响应灵敏度达到280.2%/(kA/m)。磁畴观察发现,随退火过程中拉应力的施加,薄带表层横向带状畴内部逐渐形成细小纵向畴,同时横向带状畴逐渐向纵向偏转,表明对于具有负磁滞伸缩系数的Co基薄带,焦耳-应力退火可以促进薄带内衍生纵向细畴,且纵向拉应力的施加,增强了薄带的纵向各向异性。因此,焦耳-应力退火改善了薄带的低频纵向驱动GMI效应,磁场响应灵敏度也大幅度提高。     

Fe-Si-B-P-Mo系高饱和磁感应强度非晶软磁合金

通过在Fe-Si-B-P合金体系中微合金化添加Mo元素,并提高铁含量,成功制备了具有较强非晶形成能力和优异软磁性能的非晶软磁合金。研究发现,Mo元素微合金化能有效提高合金的非晶形成能力,1%的Mo可以将该非晶合金体系的Fe含量极限提高到84%以上,从而得到了饱和磁感应强度(Bs)高达1.63 T的非晶合金。其中Fe80Si4.75B9.5P4.75Mo1非晶合金可以铸造形成非晶块体样品,临界直径达到1mm,饱和磁感应强度达到1.54 T,矫顽力为1.9 A/m。在整个成分范围内,该合金体系都具有1.9~5.1 A/m的低矫顽力和高于传统Fe-Si-B合金的饱和磁感应强度(Bs),具有较好的应用前景。     

非晶Fe_(52)Co_(34)Hf_7B_6Cu_1合金的形成与热稳定性研究

采用熔体单辊急冷法制备了非晶合金Fe52Co34Hf7B6Cu1薄带,在非晶合金制备过程中,铜辊表面线速度分别为49,45m/s,合金中的元素B分别以纯B和FeB形式加入。研究表明,在同一冷速(49m/s)的情况下,加入纯B制备的非晶态合金的晶化激活能较加入FeB略高,其热稳定性较好;而同样加入FeB制备的非晶合金,冷速较快时(49m/s)制备的非晶态合金晶化激活能较高,其热稳定性较好。     

磁控溅射制备Cu/FeNi复合丝的巨磁阻抗效应

采用磁控溅射法制备了Cu/FeNi复合结构丝,并对其结构及巨磁阻抗(GMI)效应进行了研究.结果表明,Cu/FeNi复合结构丝具有良好的GMI效应,在较低频率下观察到的最大磁阻抗变化可达247.4%,同时发现FeNi铁磁层厚度对复合结构丝的软磁性能有重要影响,找到了复合结构丝铁磁层最佳厚度的范围,当厚度达到一定值时铁磁层内磁矩方向由环向分布转向复合丝长轴方向,表现出不同的GMI行为.     

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%。     

淬态非晶FeSiB薄带的各向异性及其巨磁阻抗效应

采用单辊快淬法制备了Fe_(75)Si_9B_(13)非晶薄带。磁阻抗测试显示,淬态非晶FeSiB合金薄带具有显著的巨磁阻抗效应(GMI),在7 MHz频率下,纵横向最大阻抗比分别达到30%和29%。磁畴结构观察表明,薄带样品磁畴结构为具有一定的横向取向的180°条形畴,易轴与样品横向夹角约为75°。磁电阻变化与样品各向异性变化没有直接关系,相比磁阻抗,磁感抗更确切地反映了磁矩转动磁化行为和样品各向异性场的大小,易轴具有一定的横向取向以及薄带各向异性在厚度方向的空间分布是影响其GMI变化特性的原因。分析了磁电阻、磁感抗对样品巨磁阻抗效应的影响,发现,低频下,磁电阻对磁阻抗变化起主要作用,随着趋肤效应增强,样品磁感抗逐渐成为影响磁阻抗变化行为的主要方面。     

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。     

Si的添加对FeNiMoB合金非晶形成能力与软磁性能的影响

利用单铜辊甩带法制备Fe40Ni38Mo4B(18-x)Six(x=0,2,4,6,8,10和12)非晶合金带材,并用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、振动样品磁强计(VSM)以及精密磁性器件分析仪研究Si元素对Fe Ni Mo BSi合金带材的非晶形成能力和软磁性能影响。结果表明,随着Si元素的添加,合金带材的矫顽力Hc先减小后增大,并在x=4时最小为5.8 A/m;Fe40Ni38Mo4B14Si4合金带材在405℃保温10 min热处理后获得较高的饱和磁化强度为112.63 A·m2/kg,在345℃保温10 min热处理后获得较低的矫顽力为7.0A/m。     

应力作用下电流退火对钴基非晶薄带的巨磁阻抗效应的影响研究

采用应力作用下的直流电流退火处理Co68.2Fe2.3Mo2Si12.5B15非晶薄带，详细讨论了应力退火前后Co基薄带的巨磁阻抗效应的变化，以及退火时间对巨磁阻抗效应的影响，研究表明：应力作用下的电流退火有利于巨磁阻抗效应的提高，并可以通过控制退火时间控制阻抗与外场变化关系曲线形状。     

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co₆₉Fe_4.5Al_1.5Si₁₀B₁₅ amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.     

Enhanced giant magnetoimpedance effect in FINEMET/TiO2 composite ribbons

In order to study the influence of semiconductors on the magnetic properties and giant magnetoimpedance effect of FINEMET ribbon, titanium dioxide coating layer with different thickness was sputtered onto the free surface of the FINEMET ribbon by RF magnetron sputtering to prepare the FINEMET/TiO₂ composite ribbons. The morphology, magnetic properties, and giant magnetoimpedance of the FINEMET/TiO₂ composite ribbons were analyzed. The results show that the GMI ratio of composite ribbons first increases and then decreases with the increase of TiO₂ layer thickness (0?~?150 nm). When the thickness of TiO₂ thin film is 100 nm, the GMI ratio reaches the maximum 57.3%, which indicates that a certain thickness of TiO₂ thin film can significantly improve the GMI effect. The result can be explained by the combined result of electromagnetic interaction and stress between TiO₂ thin film and the FINEMET ribbon.

     

Electrochemical behavior of partially crystallized amorphous Al86Ni9La5 alloys

The Al₈₆Ni₉La₅ amorphous ribbons were annealed at 503 K for different time to obtain partially crystallized alloys with the different volume fractions of α-Al phase, and the effect of the crystallization extent on the electrochemical behavior of the ribbon was investigated in 0.01 M NaCl solution. The results show that the corrosion resistance of the partially crystallized ribbons is higher than that of the as-spun ribbon with the fully amorphous structure, and the corrosion resistance of the partially crystallized alloy is strongly dependent on the volume fraction of α-Al phase. The partially crystallized ribbon containing about 20 vol% α-Al phase exhibits the highest corrosion resistance.     

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.     

保护气氛对Fe80Si9B11非晶带材表面特征及磁性能的影响

非晶合金带材的表面特征对磁性能有着重要的影响。为研究CO保护气氛对Fe₈₀Si₉B₁₁非晶带材表面鱼鳞纹的形成及非晶合金带材磁性能的影响规律,本文采用平面流铸法制备了Fe₈₀Si₉B₁₁非晶合金带材,利用金相显微镜、X射线衍射仪和磁性能测试仪研究了熔潭保护气体CO流量对非晶合金带材表面特征、微观结构及磁性能的影响。研究表明,不同CO流量条件下制备的合金带材均为非晶态,且CO流量对带材厚度几乎无影响;随CO流量增大,熔潭周围气体密度和气压降低,熔潭稳定性增强,裹入熔潭的气体变少,带材贴辊面气泡尺寸变小且数量减少,带材表面的鱼鳞纹间距增大。当CO流量为0时,带材表面比较粗糙,观察不到鱼鳞纹;当CO流量为0.25和0.5 m³/h时,带材表面鱼鳞纹间距分别为1.5、2.3 mm。随CO流量增大,由于气泡对畴壁的钉扎和鱼鳞纹细化磁畴的协同作用,使带材矫顽力和铁损降低,振幅磁导率增大;磁损耗分离结果表明,随CO流量增大,磁滞损耗降低,涡流损耗增大,且铁损降低主要由磁滞损耗降低引起的。     

Isothermal Crystallization Kinetics of an Amorphous CuTi Alloy

Isothermal crystallization kinetics ofCu_(40)Ti_(60)amorphous alloy has been studied usingdifferential scanning calorimetry(DSC).Bothas-quenched and pre-annealed ribbons were inves-tigated.For crystallization of as-quenched amor-phous ribbon in Ar,it was found that the kineticsfollows Johnson-Mehl-Avrami equation withmean Avrami exponent n=2.58,which indicatesthat crystallization of amorphous Cu_(40)Ti_(60)is athree-dimensional diffusion controlled growth pro-cess with constant nucleation rate,i.e.,primarycrystallization process.The primary phase is thetetragonal CuTi_2.The as-quenched amorphousribbons were also crystallized in air,the results re-veal that oxidation has no significant influence oncrystallization kinetics of amorphous Cu_(40)Ti_(60).The results of crystallization of pre-annealed rib-bons show a decreasing tendency of Avrami expo-nent with increasing pre-anneal time.The localactivation energy and local Avrami exponent dur-ing crystallization process of as-quenched amor-phous alloy were also examined.     

非晶态合金条带高压复合法制备大块非晶态合金

介绍一种制备大块非晶态合金的新方法－快淬非晶态合金和条带高压复合法，其原理是利用高压抑制非晶态合金的晶化过程，从而在较宽的温区通过大量均匀的粘滞流变实现快淬非晶态合金条带的全致密复合。