溅射条件下对FeSiB薄膜磁性及巨磁阻抗效应的影响

采用射频磁控溅射法,在不同溅射条件下制备了ＦｅＳｉＢ薄膜。研究了溅射条件下对薄膜应力、磁滞回线及磁阻抗效应的影响。结果表明：随着溅射氩气压强的增加,薄膜内应力从压应力变为张应力,磁滞回线的形状随溅射条件下的不同也发生改变。对磁各向异性的变化作了分析和讨论,而面内横向单轴磁各向异性的重要性在磁阻抗效应的实验中充分得到了体现。     

RE－TM磁光记录薄膜的磁场电效应研究

研究了磁性薄膜磁场电效应的测试方法，ＲＥ－ＴＭ磁光薄膜的测试样品制备、样品的磁场电效应（霍尔效应和磁阻效应）及其温度特性。实验结果表明，制备的ＴｂＦｅＣＯ薄膜的补偿点约为─３８℃。     

非晶FeSiB薄膜中的巨磁阻抗效应

采用射频溅射法在三组不同溅射条件下制备了FeSiB薄膜。测量了溅射薄膜的磁滞回线 ,并利用HP 41 94A阻抗分析仪 ,在 1～ 40MHz频率范围内研究了样品的巨磁阻抗效应。结果表明 :溅射条件对薄膜磁性能和巨磁阻抗效应影响很大 ,其中氩气压强为 6 65Pa ,磁场感生横向单轴磁各向异性的薄膜具有较好的软磁性能和较大的阻抗变化比值。一定温度下退火能够消除部分应力 ,阻抗变化的灵敏度能提高一倍。另外 ,对巨磁阻抗效应与测量磁场和薄膜易轴的相对位置取向之间的关系也作了讨论     

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。     

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%.     

软磁薄膜高频巨磁阻抗效应的理论模型

利用修正的Ｌａｎｄａｕ－Ｌｉｆｓｈｉｔｚ－Ｇｉｌｌｅｒｔ方程，对横向单轴磁各向异性软磁薄膜在高频下的有效横向磁导率做了理论推导，从而得到了关于薄膜高频阻抗的理论表达式，并与其它理论结果作了比较。结果表明，给出的有效横向磁导率表达式与其它理论结果一致。详细讨论了小尺寸薄膜中退磁场对共振频率的影响，理论计算与结果相符合。     

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％。     

溅射条件对FeSiB薄膜磁性及巨磁阻抗效应的影响

采用射频磁控溅射法,在不同溅射条件下制备了FeSiB薄膜。研究了溅射条件对薄膜应力、磁滞回线及巨磁阻抗效应的影响。结果表明:随着溅射氩气压强的增加,薄膜内应力从压应力变为张应力,磁滞回线的形状随溅射条件的不同也发生改变。对磁各向异性的变化作了分析和讨论,而面内横向单轴磁各向异性的重要性在巨磁阻抗效应的实验中充分得到了体现。     

软磁薄膜高频巨磁阻抗效应的理论模型

利用修正的Landau-Lifshitz-Gilbert方程,对横向单轴磁各向异性软磁薄膜在高频下的有效横向磁导率做了理论推导,从而得到了关于薄膜高频阻抗的理论表达式,并与其它理论结果作了比较。结果表明,给出的有效横向磁导率表达式与其它理论结果一致。详细讨论了小尺寸薄膜中退磁场对共振频率的影响,理论计算与实验结果相符合。     

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%.     

Anisotropic magnetoresistance in ferromagnetic 3d alloys

The anisotropic magnetoresistance effect in 3d transition metals and alloys is reviewed. This effect, found in ferromagnets, depends on the orientation of the magnetization with respect to the electric current direction in the material. At room temperature, the anisotropic resistance in alloys of Ni-Fe and Ni-Co can be greater than 5%. The theoretical basis takes into account spin orbit coupling and d band splitting. Other properties such as permeability, magnetostriction, and Hall voltage have no simple relationship to magnetoresistance. Anisotropic magnetoresistance has an important use as a magnetic field detector for digital recording and magnetic bubbles. Such detectors because of their small size are fabricated using thin film technology. Film studies show that thickness, grain size, and deposition parameters play a significant role in determining the percentage change in magnetoresistance. In general, the change is smaller in films than bulk materials. Several tables and graphs that list bulk and film data are presented.     

Giant magnetoresistive spin valve bridge sensor

We describe the design, fabrication, and performance of a “spin valve” magnetic field sensor based on the giant magnetoresistive effect. The sensor is a balanced, four resistor, fully biased, Wheatstone bridge network with bipolar output. The devices described here show magnetoresistance ratios ΔV/V=ΔR/R=6%, saturation fields of 25 Oe, and a Johnson limited noise floor of 2.6 μOe/(Hz)^1/2. The linearity of the device is +/-2% of the full scale amplitude, with a hysteresis of 1% over the linear range. Fabrication of this device requires a novel approach to setting the directions of the antiferromagnetic exchange layers that bias the sensor. As compared to bridges based on the anisotropic magnetoresistance effect, these devices offer superior signal amplitude and linearity. To our knowledge this is the first report of such a device     

Si作过渡层的Co/Cu/Co三明治膜中高灵敏度巨磁电阻效应和平面内磁各向异性

用高真空电子束蒸发方法制备了以半导体材料Ｓｉ 为过渡层的Ｃｏ／Ｃｕ／Ｃｏ三明治膜并研究了其巨磁电阻效应。当Ｓｉ 过渡层厚度达到０．９ｎｍ 时,三明治膜中开始出现较强的平面内磁各向异性。在Ｓｉ１．５ｎｍ／Ｃｏ ５ｎｍ／Ｃｕ ３ｎｍ／Ｃｏ ５ｎｍ结构中,在其易轴上得到了５ ．５％ 的巨磁电阻值和０．９ ％／Ｏｅ 的高磁场灵敏度。研究了过渡层Ｓｉ／Ｃｏ 界面之间的相互扩散,发现在过渡层Ｓｉ 与Ｃｏ 层间形成了ＣｏＳｉ 化合物。这个硅化物界面层诱导了三明治膜的平面内磁各向异性,从而导致了易轴上高灵敏度巨磁电阻效应。     

A hysteresis model for an orthogonal thin-film magnetometer

The operation of a ferromagnetic thin-film magnetometer using the anisotropic magnetoresistance effect in a permalloy film is discussed. Measurements showed the presence of a hysteresis effect not predicted by available models. It is shown that the sensitivity of the magnetometer is predicted by applying F.S. Greene and R.B. Yarbrough's (1970) orthogonal susceptibility model, and that the hysteresis can be explained by assuming dispersion in the magnitude of anisotropy. The orthogonal susceptibility model must be evaluated numerically, accounting for a finite driving field. The effect of an inhomogeneous demagnetizing field in the film is discussed in relation to magnitude dispersion of the anisotropy     

Thick film resistors in low-temperature resistance thermometry in high magnetic fields

Thick film resistors exhibit a strong dependence on temperature in the cryogenic range below 20 K. In this range the temperature coefficient of resistance is estimated to be comparable to that of commonly used resistance thermometers.The resistance change by the action of the magnetic field is observed to be only small and independent of magnetic field direction. By using these resistors in cryogenic resistance thermometry in intense magnetic field the temperature error due to the magnetoresistance is shown to be only small in comparison with frequently used sensors.According to these results thick film resistors are reported to offer an interesting alternative in cryogenic resistance thermometry within intense magnetic fields.     

诱导磁场对化学沉积Co-Ni-P薄膜磁性能的影响

采用化学湿法沉积技术制备了CoNiP磁性薄膜,研究了施镀过程中的诱导磁场对CoNiP薄膜磁性能和结构的影响。研究结果表明,随着施加诱导场强度的增加,CoNiP薄膜的矫顽力先增加,然后减小;当磁场强度为1300 Oe时,薄膜的矫顽力达到了751.7 Oe,比未施加磁场时提高了约28%。X射线衍射结果表明,Co-N-i P薄膜晶粒沿磁场方向生长,其c轴沿薄膜的轴向形成了很强的Co(002)织构。扫描电子显微镜表面形貌观察表明,随着磁场强度的增加,胞状颗粒逐渐增多,晶粒尺寸变小,颗粒之间结合紧密。诱导磁场对CoNiP薄膜的磁性能有良好的促进作用,这为进一步开发高性能的磁电传感器奠定了一定基础。     

A spin-valve-like magnetoresistance of an antiferromagnet-based tunnel junction

A spin valve is a microelectronic device in which high- and low-resistance states are realized by using both the charge and spin of carriers. Spin-valve structures used in modern hard-drive read heads and magnetic random access memoriescomprise two ferromagnetic electrodes whose relative magnetization orientations can be switched between parallel and antiparallel configurations, yielding the desired giant or tunnelling magnetoresistance effect. Here we demonstrate more than 100% spin-valve-like signal in a NiFe/IrMn/MgO/Pt stack with an antiferromagnet on one side and a non-magnetic metal on the other side of the tunnel barrier. Ferromagneticmoments in NiFe are reversed by external fields of approximately 50 mT or less, and the exchange-spring effect of NiFe on IrMn induces rotation of antiferromagnetic moments in IrMn, which is detected by the measured tunnelling anisotropic magnetoresistance. Our work demonstrates a spintronic element whose transport characteristics are governed by an antiferromagnet. It demonstrates that sensitivity to low magnetic fields can be combined with large, spin-orbit-coupling-induced magnetotransport anisotropy using a single magnetic electrode. The antiferromagnetic tunnelling anisotropic magnetoresistance provides a means to study magnetic characteristics of antiferromagnetic films by an electronic-transport measurement.     

Magnetic-field-sensing materials composed of metal-semiconductor hybrid nanostructures

A huge positive magnetoresistance effect, about 4 orders of magnitude at room temperature, was discovered in metal-semiconductor hybrid nanostructures. The hybrid material consisting of metallic nanostructures that are fabricated on a GaAs substrate by ultra-high vacuum deposition method exhibits magnetic field-sensitive current-voltage characteristics. When a constant voltage above the threshold value, is applied to the film, a very steep change in the current, which we term magnetoresistive switch, is driven by the huge magnetoresistance effect under a relatively low magnetic field at room temperature. The magnetoresistance effect is very sensitive to the nanoscale morphology of the hybrid film; in other words, one can control the magnetoresistance function at will by modifying the nanostructure of this material. The origin of the magnetoresistive switch effect and its possible application as a magnetic field sensor is discussed.     

On‐Chip Magnetic Platform for Single‐Particle Manipulation with Integrated Electrical Feedback

Methods for the manipulation of single magnetic particles have become very interesting, in particular for in vitro biological studies. Most of these studies require an external microscope to provide the operator with feedback for controlling the particle motion, thus preventing the use of magnetic particles in high‐throughput experiments. In this paper, a simple and compact system with integrated electrical feedback is presented, implementing in the very same device both the manipulation and detection of the transit of single particles. The proposed platform is based on zig‐zag shaped magnetic nanostructures, where transverse magnetic domain walls are pinned at the corners and attract magnetic particles in suspension. By applying suitable external magnetic fields, the domain walls move to the nearest corner, thus causing the step by step displacement of the particles along the nanostructure. The very same structure is also employed for detecting the bead transit. Indeed, the presence of the magnetic particle in suspension over the domain wall affects the depinning field required for its displacement. This characteristic field can be monitored through anisotropic magnetoresistance measurements, thus implementing an integrated electrical feedback of the bead transit. In particular, the individual manipulation and detection of single 1‐μm sized beads is demonstrated.     

FeNHf软磁薄膜中磁各向异性对太赫兹波调控的研究

本文制备了具有磁各向异性的纳米FeNHf软磁薄膜,表征了FeNHf薄膜的微结构、磁性能、微波磁动力学行为和磁各向异性对太赫兹波传输特性的影响.FeNHf薄膜的难轴方向具有410的磁导率,易轴方向没有磁导率信号,磁各向异性场为2537.65 A/m.FeNHf薄膜在1.04 THz时出现了共振吸收峰,当调控磁化强度方向分...