臺灣博碩士論文加值系統

本論文利用空間與時間解析光譜研究不同幾何形狀的鎳薄膜在外加磁場下瞬時反射率變化(∆R/R)之二維分布。從瞬時反射率變化的信號，我們清楚觀察到兩個弛緩過程，一個為較快的電子-聲子散射過程；另一個為較慢的自旋-晶格散射過程。實驗結果顯示，在改變外加磁場強度下，電子-聲子散射過程並不受影響，但自旋-晶格散射過程卻與外加磁場有密切的關係，隨著外加磁場越強，則自旋-晶格散射時間即越長。除此之外，在不同幾何形狀與尺寸下，也可經由空間與時間解析光譜觀測其磁矩在受磁場極化後的動力學行為。

In this thesis, we study the ultrafast dynamics of Nickel thin films with various microstructures using spatially and time-resolved femtosecond spectroscopy under different magnetic fields. From the transient reflectivity changes (∆R/R) in Nickel thin films, we observed two relaxation processes, one is the electron-phonon scattering process with ~10 ps, the other is the spin-lattice scattering process with ~100 ps. The electron-phonon scattering process is independent of the magnetic field. On the contract, the spin-lattice scattering process is strongly dependent on the magnetic field. Moreover, the microstructure-dependent ultrafast dynamics of Nickel thin films also can be revealed by this spatially and time-resolved femtosecond spectroscopy.

中文摘要 i
Abstract in English ii
致謝 iii
目錄 iv
圖目錄 vii
表目錄 xiii
第一章 緒論 1
1.1鎳鐵材料的發展與簡介 1
1.2研究動機 2
第二章 磁性材料介紹 3
2.1磁性材料簡介 3
2.1.1單一磁區(single domain) 5
2.1.2混合磁區(multi domain) 6
2.1.3漩渦磁區(vortex domain) 7
2.2微米級磁性材料陣列製備 8
2.2.1電子束微影技術 9
2.2.2光微影技術 13
第三章 載子弛緩機制與時間解析光譜顯微系統 15
3.1載子弛緩機制 16
3.1.1載子-載子散射(carrier-carrier scattering) 17
3.1.2載子-聲子散射(carrier-phonon scattering) 17
3.1.3自旋-晶格散射(spin-lattice scattering) 18
3.2時間解析飛秒光譜原理 19
3.3時間解析飛秒技術光譜顯微系統架構 22
3.3.1系統之時間解析度 25
3.3.2系統之空間解析度 26
3.3.3二維光譜量測方式 27
3.4外加磁場均勻度 29
第四章 實驗結果與討論 33
4.1空間中不同位置之瞬時反射率變化(∆R/R) 33
4.2弛緩時間分析 43
4.3不同形狀鎳薄膜的量測結果 47
4.3.1方形鎳薄膜 47
4.3.2圓形鎳薄膜 60
4.3.3線形鎳薄膜 64
第五章 結論 69
參考文獻 70

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