系統識別號 | U0002-0408201611431100 |
---|---|
DOI | 10.6846/TKU.2016.00141 |
論文名稱(中文) | 利用同步輻射技術研究不同形貌之矽基板La0.7Sr0.3MnO3/Si對於磁性和錳價態之間交互作用的影響 |
論文名稱(英文) | Studying interplay between Mn valency and magnetization in Si nanosubstrate-modified La0.7Sr0.3MnO3 thin films by X-ray Absorption Spectroscopy |
第三語言論文名稱 | |
校院名稱 | 淡江大學 |
系所名稱(中文) | 物理學系碩士班 |
系所名稱(英文) | Department of Physics |
外國學位學校名稱 | |
外國學位學院名稱 | |
外國學位研究所名稱 | |
學年度 | 104 |
學期 | 2 |
出版年 | 105 |
研究生(中文) | 方楚涵 |
研究生(英文) | Chu-Han Fang |
學號 | 602210170 |
學位類別 | 碩士 |
語言別 | 繁體中文 |
第二語言別 | |
口試日期 | 2016-06-20 |
論文頁數 | 48頁 |
口試委員 |
指導教授
-
彭維鋒
委員 - 杜昭宏 委員 - 邱昭文 |
關鍵字(中) |
鑭鍶錳氧 吸收光譜 X光吸收之圓二向性 |
關鍵字(英) |
LSMO XANES EXAFS XMCD |
第三語言關鍵字 | |
學科別分類 | |
中文摘要 |
本文主要利用X光光譜探討不同形貌之矽基板對La0.7Sr0.3MnO3/Si的影響。由場效發射式掃描電子顯微鏡 (SEM) 及超導量子干涉儀 (SQUID) 之結果推測樣品晶粒尺寸的變化與其飽和磁化強度以及磁化現象有所關連。進一步藉由錳L3,2-edge以及氧K-edge近邊吸收光譜得知由氧缺陷所造成的錳二價離子以非等量的形式存在於不同形貌矽基板的常態錳三、四價樣品中。另一方面,由錳L3,2-edge邊磁圓偏振光譜中發現此錳二價離子會因為含量的不同,產生相異的磁耦合作用。藉由以上量測包含SEM, X光光譜以及磁性相關技術,推斷樣品在不同形貌矽基板中所導致不同的邊界或缺陷效應,會造成錳二價與錳三、四價離子兩者之間的含量比例在不同樣品中的差異。而此含量比例與樣品中飽和磁化強度並非呈現完全的線性關係,這暗示錳二價在樣品中會造成磁性不穩定的狀態,除了降低鐵磁性的效應, 如: 磁死層(magnetic dead layer)之外,尚存在其他影響磁耦合的因子。 |
英文摘要 |
This investigation of x-ray spectroscopy is focused on the series samples of La0.7Sr0.3MnO3/n+-Si with different morphology. The results of scanning electron microscope (SEM) and superconducting quantum interference device (SQUID) show that the magnetism is basically associated with the grain size of each sample. The existence of the various amount of Mn2+ between these generally Mn3+/4+-doped samples is observed by Mn L3,2-edge and O K-edge x-ray absorption near edge structure (XANES). Based on XANES, this amount of Mn2+ is strongly related to the oxygen defect. On the other hand, Mn L3,2-edge X-ray magnetic circular dichroism (XMCD) was carried out for the magnetic coupling which is sensitive to amount of Mn2+. According to the measurements above including SEM, x-ray and magnetism related techniques, the Si substrates with different morphology cause the change of Mn valence state with more or less amount of Mn2+ in each sample via the various defects or boundary conditions. However, the incompletely linear relationship between ferromagnetism and amount of Mn2+ implies that this amount of Mn2+ induces a magnetically unstable state. Except the reduction of ferromagnetic coupling, e.g. magnetic dead layer (MDL), there are still some other factors left to influence magnetic coupling. |
第三語言摘要 | |
論文目次 |
目錄 致 謝 I 中文摘要 II 英文摘要 III 目錄 IV 圖表目錄 VI 第一章、緒論 1 第二章、X光吸收光譜簡介 4 (一)、吸收邊緣與E0值 6 (二)、 X光吸收近邊緣結構(X-ray Absorption Near Edge Structure、XANES) 7 (三)、延伸X光吸收精細結構(Extended X-ray Absorption Fine Structure、EXAFS) 8 (四)、實驗方法 13 (五)、數據分析 17 第三章、X光磁圓偏振二向性簡介 (X-ray Magnetic Circular Dichroism、XMCD) 21 (一)、理論模型 21 (二)、實驗方法 22 第四章、實驗數據分析與討論 25 (一)、樣品製備與基本量測 25 (二)、X光吸收近邊緣結構 (X-ray Absorption Near Edge Structure、XANES)之分析 31 (三)、X光磁圓二向性能譜 (X-ray Magnetic Circular Dichroism、XMCD)之分析 38 (四)延伸X光吸收精細結構 (Extended X-ray Absorption Fine Structure、EXAFS)之分析 44 第五章、結論 46 參考文獻 47 圖表目錄 圖1-1 LSMO/ n+-Si NTs薄膜文獻之SEM表面幾何結構圖與示意圖 3 圖1-2 LSMO/Si薄膜樣品文獻之定磁場變溫磁化率 3 圖2-1光子能量與銅吸收截面關係圖 5 圖2-2 XANES與EXAFS分界圖 10 圖2-3光電子平均自由路徑與能量關係圖 10 圖2-4單一散射與多重散射之圖像 (a)為單一散射路程示意圖 (b)為多重散射路程示意圖 11 圖2-5射出電子受鄰近原子的背向散射,而產生干涉現象 (a)建設性干涉 (b)破壞性干涉 12 圖2-6 X光吸收光譜實驗示意圖 14 圖2-7三種光譜量測方法 16 圖2-8 X光吸收光譜之數據分析流程 17 圖 3-1 Ni L3,2-edge 吸收光譜。實線和虛線分別表示 Ni 對正磁場和負磁場的 X 光吸收光譜。 24 圖3-2 Ni L3,2-edge XMCD 譜圖 24 圖4-1 (a)、(b) LSMO 薄膜之X光繞射圖 28 圖4-2 LSMO鈣鈦礦結構圖與錳氧八面體示意圖 28 圖4-3分別為TF90、TF60以及NTs180之頂視圖(a)-(c)與側視圖(d)-(f) 29 圖4-4為LSMO/Si薄膜定磁場變溫磁化率的量測結果 30 圖4-5 LSMO/Si薄膜角度變化與標準樣品歸一化後的Mn K-edge XANES 32 圖4-6 LSMO/Si薄膜與標準樣品歸一化後的TEY Mn L3,2-edge XANES 33 圖4-7 LSMO/Si薄膜與置放在空氣中兩個月歸一化後的Mn L3,2-edge XANES 35 圖4-8 (a)室溫之 LSMO/Si薄膜O K-edge TFY,(b)Si基板O K-edge TFY,(c)高斯峰擬合O 2p之未佔據態與Mn 3d之混成軌域與面積的積分 37 圖4-9 (a) T=300K下LSMO/Si薄膜在正負磁場下之Mn L3,2-edge及XMCD譜圖 40 圖4-9 (b) T=80K下LSMO/Si薄膜在正負磁場下之Mn L3,2-edge及XMCD譜圖 41 圖4-10為TEY Mn L3-edge以MnO與LSMO(Bulk)擬合Mn2+在各樣品中所佔的百分比 42 表4-1 LSMO/Si薄膜TEY之Mn價數與XMCD強度之百分比 43 圖4-11 LSMO/Si薄膜與放置空氣中一個月定磁場變溫磁化率量測 43 圖4-12 Mn K-edge EXAFS傅立葉轉換圖 45 |
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