兰州大学机构库 >物理科学与技术学院
图形化FeTa薄膜的磁各向异性调控和磁化翻转机制研究
Alternative TitleTuning the Magnetic anisotropy and magnetization reversal mechanism investigation of patterned FeTa films
马金花
Thesis Advisor席力
2013-05-29
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword软磁薄膜 磁控溅射 磁化翻转机制 光刻
Abstract   随着器件向微型化、高频化的发展,对软磁材料高频磁性能的要求越来越高,这要求软磁材料有较高的饱和磁化强度、磁导率、电阻率和磁各向异性场,以使得材料具有较高的截止频率。为了满足磁性薄膜器件的高频要求,共振频率在GHz以上的薄膜材料已成为此领域的研究热点。    本论文使用直流磁控溅射的方法,在玻璃衬底上制备了厚度t = 130 nm的Cu/FeTa/Ta薄膜,并用光刻的方法处理形成一系列具有不同长度(L)和宽度(W)的条带阵列。分别用X射线衍射仪(XRD)测量了样品的晶体结构,利用原子力显微镜测量了样品的表面形貌和粗糙度,使用磁力显微镜观察了样品的磁畴结构,使用振动样品磁强计测试了样品室温下的整体磁性;用磁光克尔效应测量了条状样品的局部磁性;用短路微扰传输线法测量了样品的高频特性。结论如下:    1、制备态连续薄膜形成了bcc结构的FeTa合金,由谢乐公式和最强峰的半高宽估算FeTa薄膜样品中FeTa晶粒尺寸约为15.7nm. 磁性测量表明该样品是各向同性的,矫顽力Hc约为9.8 Oe,饱和磁化强度4Ms为19 kGs,具有较好的软磁性能。    2、为了研究刻蚀条带长度对样品磁各向异性的影响,对样品进行光刻处理,将连续薄膜刻蚀成宽度相同长度不同的条带阵列,结果表明当长宽比从1:1依次变化到167:1时,样品的面内单轴各向异性逐渐变得明显,当长宽比达到20:1之后,磁滞回线基本不再变化,我们认为此时磁矩基本沿着易轴排列,并且其各向异性场是一个常数,不会随着长宽比的增大而增大。这是由于条带沿宽度方向的退磁因子为t/W是一个常数而导致的。    3、为了研究刻蚀条带宽度对样品磁各向异性的影响,同样对样品进行光刻处理,将连续薄膜刻蚀成长度不变宽度变化的条带阵列,结果表明所有的样品都具有明显的面内单轴各向异性,随着条带宽度的逐渐减小,样品的各向异性场逐渐增大,并且与条带宽度的倒数成正比,即样品的各向异性场与长宽比成正比。这是由于条带沿宽度方向的退磁因子t/W随W的减小而增大导致的。    4、对样品的磁化翻转机制进行的研究表明: 在易轴附近较大角度范围内,其磁化翻转过程是通过畴壁成核或畴壁定扎来实现的,矫顽力的变化规律符合Kondorsky模型;在难轴附近其磁化翻转过程是通过磁矩的一致转动来实现的,其变化规律符合Stoner-Wohlfarth模型. 而在全角度范围内,实验数据和两相模型曲线都吻合的较好,所以我们用两相模型对一系列条带宽度变化的样品进行拟合,可以看出随着条带宽度减小,各向异性变化,矫顽力峰值所对应的角度向大角度方向移动,并且实验数据和理论曲线拟合的更好。    5、高频磁性的测量表明,随着条带长宽比的增大,其共振频率向高频方向移动,对长宽比为500:1的样品,其共振频率超过7GHz. 因此通过改变条带的长宽比可实现薄膜各向异性的调控,进而对高频软磁性能的调控。
Other Abstract  With miniaturization and high frequency of electromagnetic devices, the requirements for high frequency soft magnetic thin films are more demanding. This requires that the materials have a higher saturation magnetization, permeability, the resistivity and appropriately magnetic anisotropy field , so that the materials has a higher cut-off frequency. In order to meet the requirements of high-frequency magnetic thin film device, the film materials with the resonance frequency in the GHz or above have become research hotspots in this field.   In this work, A series of FeTa films with the thickness of 130 nm have been fabricated on glass substrates by magnetron sputtering at ambient condition. Conventional optical lithography was used to fabricate the strip array with different length and width. The crystal structure of the samples was examined using X-ray diffraction (XRD) with Cu-Ka radiation. We used atomic force microscope (AFM) to observe the surface topographies, At the same time, we use magnetic force microscope (MFM) to study the domain structure of samples. Magnetic properties of the FeTa films were measured by a vibrating sample magnetometer (VSM) (MicroSense EV-9) with the magnetic field resolution and sweep rates around 7.8 A/m and 96.0 A/m per second, respectively. A Durham micro-focused Magneto-optical Kerr Effect (MOKE) equipment NanoMOKE 2TM was utilized to study the magnetic properties of a single strip with a 3 m sized laser spot focused on the middle and end parts of the strip, respectively. The longitude Kerr signal was recorded with the applied field along the length direction of strips. The high frequency properties were observed by using the shorted microstrip transmission-line perturbation method. All measurements were performed at room temperature. The results are shown as follow:   1、The as deposited continuous FeTa films show the isotropic magnetic properties with crystallized bcc structure and FeTa grain size around 15.7 nm. The saturation magnetization (4πMs) and coercivity (Hc) obtained from the hysteresis loop are 19 kGs and 9.8 Oe, respectively.   In order to study the influence of the length of magnetic strip on magnetic anisotropy, we etch the continuous films into strip arrays with the length of strip from 30 m to 2500 m while the widths of strip are kept at 30 m. The results indicate that the in plane uniaxial anisotropy of sample gradually become strong with change the aspect ratio from 1:1 to 167:1. When th...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229243
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
马金花. 图形化FeTa薄膜的磁各向异性调控和磁化翻转机制研究[D]. 兰州. 兰州大学,2013.
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