臺灣博碩士論文加值系統

鐵磁性物質的幾何性狀大小會決定其內部的磁區結構，對於次微米磁性圓盤而言，直徑和厚度會決定其磁區結構為單一磁區(single domain)，漩渦磁區(vortex domain)或是混合磁區(multi-domain)，我們實驗主要的目的是利用磁電阻量測的方式來探討漩渦磁區的物理特性。
透過電子束微影技術製作了直徑範圍從0.5um到1.9um，厚度48nm以及38nm的permalloy磁性圓盤，在這個範圍內的磁性圓盤在沒有外加磁場時，內部磁矩排列呈現漩渦磁區結構。我們將圓盤製作在30nm厚的下電極金上，金的寬度等於圓盤直徑，並利用四點量測法量測電阻；磁電阻量測包含兩種安排：電流平行外加磁場(LMR)和電流垂直外加磁場(TMR)。
漩渦磁區隨著外加磁場而產生的變化透過異向性磁阻效應(AMR effect)會充分的反映在我們的磁電阻量測上，並以此我們可以得知漩渦磁區的annihilation field和nucleation field；在我們的量測結果中，annihilation field以及nucleation field會隨著圓盤直徑的增加而減少。
當漩渦磁區的核(vortex core)在外加磁場下移動時，我們將其視為剛體，表示漩渦磁區的移動並不會破壞其磁矩和核(vortex core)的相對位置和方向；利用剛體模型算出的annihilation field，可以在定量上解釋由磁電阻遲滯曲線量測所得到的annihilation field對圓盤直徑的關係，雖然用剛體模型所算出的nucleation field只有磁電阻遲滯曲線得到的四分之一，但是在定性上理論所預期的nucleation field對圓盤直徑的關係和磁電阻量測所得到的是一致的。

The magnetic domain structure of a magnetic disk depends on its geometrical factors such as thickness and diameter and can be single domain, vortex domain or multi-domain. The vortex domain structure is mostly observed in a sub-micron permalloy disk. In this thesis, we investigate the vortex domain by the magneto-resistance measurement.
We prepare two series of permalloy disks with diameter ranging from 0.5um to 1.9um by e-beam lithography. The thickness of one series is 38nm and the other is 48nm at remanence. The domain structure of permalloy disk with geometrical like this is vortex domain. In order to make an electric measurement, several identical disks are distributed atop a 30nm thick Au strip with a width same as the disk diameter. Contact configuration is arranged for a four-terminal electrical measurement. The magneto-resistance measurement are made in two configurations. In LMR, current is parallel to external magnetic field. In TMR current is perpendicular to external field.
Magnetization can be well described by anisotropic magneto-resistance effect (AMR) resulting in the exploration of magnetization reversal of domain configuration of the permalloy disk. We can obtain annihilation field and nucleation field from the measurement. Our data show both nucleation field and annihilation field increases with decreasing disk diameter.
The domain of disk in applied magnetic field is treated as off-center rigid vortex structure; i.e., the vortex keep its spin distribution while being displaced. The rigid vortex model yields the analytical expressions for the size dependent vortex nucleation and annihilation fields.
The simulation gives a quantitative agreement with the vortex annihilation field that obtained form MR curves. The vortex nucleation field from the experiment data is about one quarter of the theoretical prediction, however, it has a qualitative dependence on its geometry as expected.

第一章 序論 1
第二章 磁性圓盤(magnetic disk)研究的文獻回顧以及理論 3
2-1 次微米磁性圓盤的磁區結構 3
2-1.1 漩渦磁區(vortex domain) 5
2-1.2 單一磁區(single domain) 12
2-1.3 磁區分界點 13
2-1.4 混合磁區(Multi-domain) 14
2-2 決定磁區結構的能量 16
2-2.1 交互作用能(Exchange energy) 16
2-2.2 靜磁能(Magnetostatic energy) 17
2-2.3 異向性能(Anisotropic energy) 17
2-2.4 Zeeman energy 18
2-2.5 圓盤直徑和厚度對磁區的影響 18
2-3 漩渦磁區(vortex domain)的能量 21
2-3.1 剛體模型(rigid model) 21
2-3.2 漩渦磁區能量 22
2-3.3 能量改變對漩渦磁區的影響 23
2-3.4 Annihilation field 26
2-3.5 Nucleation field 27
2-4 異向性磁阻(AMR effect) 29
第三章 樣品製作及量測 30
3-1 微影技術 31
3-1.1 電子束微影技術 31
3-1.2 光微影技術 36
3-1.3 熱蒸鍍技術 37
3-2 樣品製作 39
3-3 低溫系統 46
3-3.1 低溫系統裝置簡介 46
3-3.2 低溫系統操作步驟-降溫 47
3-4.3 低溫系統操作步驟-更換樣品 48
3-5 樣品量測 50
第四章 實驗結果與討論 53
4-1 磁電阻曲線反映漩渦磁區的翻轉 53
4-1.1 LMR遲滯曲線的理論預期 53
4-1.2 TMR遲滯曲線的立論預期 54
4-1.3 Nucleation field和Annihilation field 54
4-1.4 實驗量測出來的遲滯曲線 55
4-2 Annihilation field和Nucleation field與磁盤
幾何形狀 60
4-2.1 Nucleation field 60
4-2.2 Annihilation field 61
第五章 結論 64
文獻索引 66

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