臺灣博碩士論文加值系統

本論文主題為次微米線寬橢圓環與半環磁性圖案的磁光科爾效應研究，利用微磁光科爾效應儀(MOKE)、磁力顯微鏡(MFM)、微磁學模擬軟體(OOMMF)進行實驗與分析。次微米線寬樣品的製作，經由電子束微影及磁控濺鍍與舉離等步驟而完成，線寬最細可達50奈米。由MOKE量測NiFe圓環陣列並與文獻結果比較，發現磁化暫穩態的翻轉場與樣品線寬及膜厚有密切的關聯性。而針對半環形的實驗結果發現，半環形短軸的磁滯曲線有類似圓環形樣品的二階翻轉(two step switching)特性，當線寬越細，鐵磁層膜厚越大時，此現象更為顯著。藉由加熱到大於反鐵磁層Neel溫度，並外加磁場於鐵磁(NiFe)/反鐵磁(IrMn)雙層結構的半環形陣列，進行退火處理，其中外加磁場方向便決定單向異向性方向，改變MOKE量測磁場與單向異向性的夾角(θ)進行量測，發現交換偏移場(exchange bias)並不正比於cos(θ)，因此推論形狀異向性在此具有重要的影響力。改變橢圓環形間的距離，發現間距越遠，渦旋態(vortex state)能維持的越久，且磁化由渦旋態到洋蔥態的翻轉場隨間距加大而遞增，而由洋蔥態到渦旋態的翻轉場則隨間距加大而遞減，這主要是因為相鄰近橢環之間，磁壁耦合的作用強弱所造成的差異。

Sub-micron line width magnetic oval rings and half-rings were investigated by Magneto-Optical Kerr Effect (MOKE) magnetometer, Magnetic Force Microscopy (MFM) and micro magnetic simulation. The sub-micron line width samples were fabricated by electron-beam lithography, dc magnetron sputtering and lift-off process. The line width was varied down to 50 nm.
The magnetic switching behavior of arrays of NiFe rings and half rings elements as functions of the film thickness and line width was studied in detail. Two-step switching behavior, as in the ring shape, was observed when external field was in the short axis for single half-ring films. The two stable magnetic states, onion and vortex states, were observed in thick film and narrow width samples.
For NiFe/IrMn double layer structures, the uni-directional anisotropy could be controlled by field cooling the samples. The exchange field strength did not follow a cosine curve when the external field was rotated in the sample plane. It could be attributed to the competition between the shape and the exchange anisotropies.
To study the interaction between individual single layer oval rings,
the edge to edge distance x of the oval rings in the long axis direction was varied from 0.1 to 2 µm. The vortex to onion states switching field increased, and the onion to vortex states switching field decreased with increasing x. The various transitions between the different equilibrium states in oval rings are affected by the inter-ring domain wall coupling.

中文摘要 Ⅰ
英文摘要 Ⅱ
目錄 Ⅲ
圖目錄 Ⅴ
表目錄 Ⅸ
第一章 簡介...............................................1
1-1 研究動機與論文簡介....................................1
1-2 形狀異向性 (shape anisotropy).........................5
1-3 交換偏移場(Exchange Bias)............................9
第二章 文獻回顧..........................................12
2-1 磁光科爾效應磁量儀相關文獻...........................12
2-2 磁化暫穩態相關文獻...................................16
2-3 交換偏移與形狀異向性對鐵磁/反鐵磁交換耦合系統之影響..20
2-4 環形陣列間的磁性交互作用.............................24
第三章 基本原理..........................................26
3-1 法拉第效應(Faraday Effect)...........................26
3-2 磁光科爾效應(Magneto-Optical Kerr Effect)............30
3-3 偏振棱鏡(Polarizing Prisms)..........................32
第四章 實驗裝置與樣品製程................................36
4-1 磁光柯爾效應磁量儀...................................36
4-2 Vector-MOKE 實驗裝置.................................42
4-3 磁力顯微鏡...........................................44
4-4 樣品製程.............................................44
第五章 實驗結果與討論....................................47
5-1 圓環型陣列樣品.......................................47
5-2 Ni80Fe20 半環形陣列樣品..............................54
5-2-1 半環形陣列樣品形狀異向性...........................54
5-2-2 二階翻轉...........................................59
5-3 NiFe 橢圓環形陣列樣品................................63
5-4 Ni80Fe20/IrMn 雙層半環形陣列.........................69
5-4-1 形狀異向性.........................................69
5-4-2 半環形陣列交換偏移場的實驗結果.....................76
5-4-3 NiFe/IrMn 半環陣列二階翻轉特性.....................84
5-4-4 Vector-MOKE 量測結果...............................88
5-5 物鏡聚焦雷射光點量測結果.............................93
第六章 結論..............................................96
參考文獻.................................................99

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