Cu对NiFe／Cu／NiFe层状薄膜的巨磁阻抗效应影响的研究

用直流磁控溅射方法制备了ＮｉＦｅ／Ｃｕ／ｎｉＦｅ层状薄膜,研究了Ｃｕ膜宽度对ＮｉＦｅ／Ｃｕ／ｎｉＦｅ层状薄膜的巨磁阻抗效应的影响,结果表明,层状薄膜的巨磁阻抗疚随Ｃｕ膜宽度发生振荡现象,并提出了一个等效电路模型直观地解释了层状薄膜增强巨磁阻抗效应的机理。     

NiFe和NiFe/Cr/NiFe薄膜的磁电阻特性与膜厚关系

本文研究了采用离子束溅射技术制备的 NiFe 薄膜及层状结构 NiFe/Cr/NiFe 薄膜的磁电阻特性与膜厚的关系。用四探针法测量薄膜的磁电阻。由实验结果得到磁电阻特性与膜厚及 Cr 夹层厚度的关系。分析了 NiFe/Cr/NiFe 膜中两层 NiFe 膜之间存在反铁磁交换耦合时,磁电阻效应显著增强的现象,NiFe/Cr/NiFe 膜各向异性磁电阻系数△ρ/ρ_(av)达5.1%。     

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%.     

FeSiB/Cu/FeSiB多层膜巨磁阻抗效应研究

用磁控溅射法在玻璃基片上制备了FeSiB/Cu/FeSiB多层膜,在100kHz～40MHz范围内研究了FeSiB/Cu/FeSiB多层膜中的巨磁阻抗效应特性.当磁场强度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3.2MHz时,在磁场强度Ha=2400A/m时巨磁阻抗变化率达到最大值13.50%;在磁场强度Ha=9600A/m时,巨磁阻抗变化率为-9.20%.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,在频率为3.2MHz,磁场强度Ha=9600A/m时,巨磁阻抗变化率可达-12.50%.     

FeSiB／Cu／FeSiB多层膜巨磁阻抗效应研究

用磁控溅射法在玻璃基片上制备了FeSiB/Cu/FeSiB多层膜,在100kHz-40MHz范围内研究了FeSiB/Cu/FeSiB多层膜中的巨磁阻抗效应特性。当磁场强度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3.2MHz时,在磁场强度Ha=2400A/m时巨磁阻抗变化率达到最大值13．50％;在磁场强度Ha=9600A/m时,巨磁阻抗变化率为－9．20％。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,在频率为3．2MHz,磁场强度Ha=9600A/m时,巨磁阻抗变化率可达－12．50％。     

[NiFe/Cu/Co/Cu]_n多层纳米线在巨磁电阻位移传感器中的应用

采用双槽电沉积法制备了巨磁电阻(Giant Magnetorsistance;GMR)材料[NiFe/Cu/Co/Cu]_n多层纳米线阵列,并以其为磁传感器芯片,设计并制备了GMR位移传感器,在不同温度下测试了其灵敏度。研究表明,该GMR位移传感器的输出电压与位移具有较好的线性关系,在10~40℃环境温度内具有良好的稳定性。与[NiF e/Cu/Co/Cu]_n多层膜作传感器芯片相比,以[NiFe/Cu/Co/Cu]_n多层纳米线作为芯片时传感器灵敏度更高。     

夹心结构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夹心结构FeNi/Cu/FeNi多层膜,并在1～40MHz范围内研究了它的巨磁阻抗效应.纵向巨磁阻抗效应先随着外加磁场的增大而迅速增加,在某一磁场下达到最大值后随磁场的增加而逐渐减小.在频率为5MHz时,Hext为0.8kA/m时巨磁阻抗效应最大值达到32.06%.另外,夹心结构多层膜表现出较大的负巨磁阻抗效应,在频率5MHz,Hext=9.6kA/m时,负最大巨磁阻抗效应可达-24.50%.     

薄膜厚度对多层膜巨磁阻抗效应的影响研究

采用磁控溅射方法在玻璃基片上制备了FeSiB／Cu／FeSiB多层膜,在100kHz～40MHz范围内研究了FeSiB薄膜厚度对FeSiB／Cu／FeSiB多层膜巨磁阻抗效应的影响。当磁场施加在薄膜的纵向时,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。当FeSiB薄膜的厚度为1．8μm时,在频率3．2MHz、磁场2．4kA／m时,多层膜巨磁阻抗效应达最大值13．5％;在磁场为9．6kA／m时,巨磁阻抗效应为-9．2％。然而,当FeSiB薄膜的厚度为1μm时,多层膜的巨磁阻抗效应在频率40MHz、磁场1．6kA／m时达最大值5．8％。另外,当磁场施加在薄膜的横向时,薄膜表现出负的巨磁阻抗效应。对于膜厚为1．8μm的FeSiB薄膜,在频率5．2MHz、磁场9．6kA／m时,巨磁阻抗效应为-12％。可见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FeSiB薄膜的厚度有关。     

热处理温度对FeCoSiB薄膜及FeCoSiB/Cu/FeCoSiB三明治膜应力阻抗效应的影响

采用DC磁控溅射法在玻璃基片上制备了FeCoSiB薄膜和FeCoSiB/Cu/FeCoSiB 三明治膜,并进行磁场退火热处理以消除残余应力和形成磁织构,提高薄膜的应力阻抗效应。薄膜的磁性能采用振动样品磁强计(VSM)进行测试,采用HP4275A 型阻抗分析仪在200kHz~10MHz频率范围内测试薄膜的应力阻抗效应。结果表明,磁场退火热处理可形成感生磁各向异性,改善薄膜的软磁性能、提高薄膜的应力阻抗效应。在温度低于300℃时,随着退火温度的增加,薄膜的应力阻抗效应增大;当退火温度超过300℃时,薄膜的应力阻抗效应随退火温度增加而降低。与Fe CoSiB单层膜相比, FeCoSiB/Cu/FeCoSiB 三明治膜应力阻抗效应较大。10MHz测试频率下,在基片末端位移为450μm时,经300℃热处理的三明治膜达到了8.3%,而单层膜仅有1.86%。当测试频率较高为10和4MHz时,薄膜的应力阻抗效应变化不大,当测试频率下降到低于1MHz时,薄膜的应力阻抗效应显著降低。     

弯曲型三明治结构FeCuNbCrSiB/Cu/FeCuNbCrSiB多层膜巨磁阻抗效应研究

利用磁控溅射方法及微细加工技术制备了弯曲型三明治结构的FeCuNbCrSiB／Cu／FeCuNbCrSiB多层膜，在频率1～40MHz下研究了多层膜的纵向和横向巨磁阻抗效应，结果表明弯曲型三明治结构多层膜的巨磁阻抗效应高于它的传统的多层膜。在频率10MHz、磁场11．94kA／m下巨磁阻抗效应达-50%。     

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.     

Perpendicular GMI Effect in Meander NiFe and NiFe/Cu/NiFe Film

We have evaluated the perpendicular giant magnetoimpedance effect (GMI) in both NiFe and NiFe/Cu/NiFe films with meander geometry in the $>$1 MHz high-frequency range. With the magnetic field, the perpendicular GMI effect shows an intense GMI peak value at a certain field. This effect is comparable to the longitudinal GMI effect in both profile and peak value amplitude. The experimental results correspond well with the predictions of a single-domain rotational magnetization model. These findings demonstrate that the deflection of the anisotropy to a perpendicular direction plays an important role in the perpendicular GMI effect.      

NiFe／Cu和NiFe／Mo多层膜的界面结构与巨磁电阻

采用磁控溅射方法制备了ＮｉＦｅ／Ｃｕ和ＮｉＦｅ／Ｍｏ多层膜。测量了厚度不同的Ｃｕ层和Ｍｏ层多层膜的磁性和磁电阻,并用电镜分析了部分ＮｉＦｅ／Ｃｕ多层膜样品。测量到ＮｉＦｅ／Ｃｕ多层膜的室温巨磁电阻随Ｃｉ层厚度振荡的第一、二、三峰。而在ＮｉＦｅ／Ｍｏ多层膜中未发现巨磁电阻效应。讨论了多层膜的界面结构对巨磁电阻效应的影响。     

Cu层和Mo层对NiFe多层膜巨磁电阻（GMR）的影响

采用磁控溅射方法制备了ＮｉＦｅ／Ｃｕ和ＮｉＦｅ／Ｍｏ两个系列的多层膜，进行了结构，磁性和磁电阻测量，并对部分ＮｉＦｅ／Ｃｕ多层膜样品作了电镜分析，对于ＮｉＦｅ／Ｃｕ多层膜，在室温下的测量到巨磁电阻随Ｃｕ层厚度振荡的第一，二三峰。在ＮｉＦｅ／Ｍｏ多层膜样品中未发现巨磁电阻效应，讨论了非磁性 多层膜的磁性，界面结构和巨磁电阻效应。     

Interface Reaction of Ta/NiFe and NiFe/Ta and the Dead Layer

The structures of Ta/Ni_(81)Fe_(19) and Ni_(81)Fe_(19)/Ta are commonly used in magnetoresistance multilayers. It is found that the thickness of dead layer in Ta/Ni81Fe19/Ta was about 1.6±0.2 nm. X-ray photoelectron spectroscopy (XPS) was used to study the interfaces of Ta/Ni_(81)Fe_(19) and Ni_(81)Fe_(19)/Ta. The results show that there is a reaction at the two interfaces: 2Ta+Ni=NiTa_2, which caused the thinning of the effective NiFe layer. Furthermore, this reaction could also explain the phenomenon that the dead layer thickness of spin valves multilayers prepared by MBE is thinner than those prepared by magnetron sputtering.     

Magnetic anisotropy of the ultrathin Fe layers in Fe/NiFe/Fe/Cu multilayers and their effect to the magnetoresistance

The effects of the deposition of ultrathin ⁵⁷Fe layers on both sides of the NiFe layers in NiFe/Cu multilayers were investigated by focusing on their structural, magnetic and magnetoresistance properties. Conversion electron Mössbauer spectroscopy measurements showed an out-of-plane magnetic anisotropy of the Fe layers. The magnetoresistance curves showed an unusual shape, where up to three peaks were observed. Eight variables computer simulations, based on a phenomenological model that considers bilinear and biquadratic couplings between layers with cubic and in-plane uniaxial anisotropies, were used in order to calculate the best-fitting magnetization curves for the NiFe/Cu and Fe/NiFe/Fe/Cu multilayers. Both model and Mössbauer spectroscopy results showed that it is the rotation of the Fe magnetic moment from out-of-plane to in-plane orientation that provokes the unusual magnetoresistance curve shape. The observed reduction of the magnetoresistance amplitude with the addition of one monolayer of Fe in the NiFe/Cu multilayer was attributed to a less-effective spin-dependent scattering that occurs at Fe/Cu and Fe/NiFe interfaces than at the NiFe/Cu interfaces.     

NiFe／Co／Cu／Co结构自旋阀GMR效应及Co夹层的影响研究

用射频磁控溅射发射法成功制备了ＮｉＦｅ／Ｃｕ／Ｃｏ自旋阀多层膜材料,改变Ｃｕ层的厚度,研究材料的ＧＭＲ效应与Ｃｕ层厚度的关系,结果表明Ｃｕ为２．５ｎｍ时样品的ＭＲ值最大,其磁电阻效应ＭＲ可达１．６％,在ＮｉＦｅ和Ｃｕ之间插入一Ｃｏ薄夹层,通过对不同温度厚度Ｃｏ夹层的样品的ＭＲ曲线及磁滞回线的研究,讨论了Ｃｏ夹层对样品磁电阻的影响并分析了原因,结果表明插入适当的Ｃｏ层将提高材料的磁电阻效应,可达２．     

Effect of Cu surface segregation on properties of NiFe/FeMn bilayers

The films of NiFe/FeMn with Ta and Ta/Cu buffer layers were prepared by magnetron sputtering. Results show that the exchange bias field of NiFe/FeMn films with Ta/Cu buffer is lower than that of the films with Ta buffer. The crystalline texture, surface roughness and element distribution of these two sets of samples were examined, and there is no apparent difference for the texture and roughness. However, the segregation of Cu atoms on the surface of NiFe in the trilayer of Ta/Cu/NiFe has been observed by using the angle-resolved X-ray photoelectron spectroscopy. The decrease of the exchange bias field for NiFe/FeMn films with Ta/Cu buffer layers is mainly caused by the diffusion of Cu atoms through NiFe layer, which stayed at the interface of NiFe/FeMn film or even intruded into FeMn layer. The present results indicate that Cu segregation through NiFe layer should be suppressed in order to improve the exchange bias field in giant magnetoresistance spin valves with Cu spacer.     

Asymmetry of Magnetization Reversal of Pinned Layer in NiFe/Cu/NiFe/IrMn Spin-Valve Structure

Two types of asymmetry in giant magnetoresistance (GMR) are observed which are not related to a training effect, but indicate different mechanisms of magnetization reversal of the pinned layer in spin-valve (SV) structures for ascending and descending field scans. GMR, exchange bias and coercivity in Si/Ta/NiFe/Cu/NiFe/IrMn/Ta SV-structures were investigated as functions of the thickness of the nonmagnetic spacer. The spacer thickness effects are discussed in correlation with layers microstructure and interfaces morphology variations.     

Template-grown NiFe/Cu/NiFe nanowires for spin transfer devices

We have developed a new reliable method combining template synthesis and nanolithography-based contacting technique to elaborate current perpendicular-to-plane giant magnetoresistance spin valve nanowires, which are very promising for the exploration of electrical spin transfer phenomena. The method allows the electrical connection of one single nanowire in a large assembly of wires embedded in anodic porous alumina supported on Si substrate with diameters and periodicities to be controllable to a large extent. Both magnetic excitations and switching phenomena driven by a spin-polarized current were clearly demonstrated in our electrodeposited NiFe/Cu/ NiFe trilayer nanowires. This novel approach promises to be of strong interest for subsequent fabrication of phase-locked arrays of spin transfer nano-oscillators with increased output power for microwave applications.