臺灣博碩士論文加值系統

本論文主要是研究以濺鍍(sputter)成長人工反鐵磁結構
MgO/CoFeB/Nb、Nb/CoFeB/MgO及MgO/CoFeB/Nb/CoFeB/MgO，
分別改變這三種結構鐵磁層或非磁性層材料的厚度，並在退火後量測磁滯曲線，探討其垂直異向性和磁性耦合的變化。
研究顯示上結構在退火後，CoFeB厚度1.2~1.6nm之間產生了垂直異向性，並且隨著CoFeB厚度的增加，方正性、矯頑場Hc、磁異向場Hk都有明顯下降，可見上結構中CoFeB的厚度對垂直異向性有很大的影響，下結構在經過退火後，幾乎所有厚度都有垂直異向性，而除了矯頑場Hc值隨著Nb厚度增加，方正性與磁異向場都極為穩定，可推斷下結構中Nb厚度的改變對垂直異向性影響不大，全結構隨著Nb厚度的增加，垂直異向性也跟著減弱。Nb=1.0、1.5nm時擁有的m1及m2變化的趨勢有一致的結果，顯示這兩個結構上下CoFeB層產生磁死層的速度十分相近，Nb=2.0nm時，在255oC~345 oC之間，m1隨著溫度上升，m2卻隨之下降，顯示在這段退火溫度其磁滯曲線不同於Nb=1.0及1.5nm。將我們的實驗數據與參考文獻進行比較後，發現耦合能、異向能及退火溫度等數值，以Nb為間隔層的人工反鐵磁結構都低於以Ru為間隔層的人工反鐵磁結構。

In this study, we deposited MgO / CoFeB / Nb, Nb / CoFeB / MgO and MgO / CoFeB / Nb / CoFeB / MgO by sputtering and grew synthetic antiferromagnetic structure. These three structures were changed ferromagnetic or non-magnetic layer thickness of the material, and in the hysteresis curves measured after annealing to explore the perpendicular anisotropy and magnetic coupling.
Studies have shown that the structure after annealing, which found that the perpendicular magnetic anisotropy (PMA) of the top structure only exist in a CoFeB thickness range from 1.2 to 1.6 nm. Squarness, coercivityfield(Hc)and magnetic anisotropy field (Hk) were decreased when thickness increases. In the top structure showing that thickness of the CoFeB structure for perpendicular anisotropy has a great influence. But, in the bottom structure which after annealing, almost all thicknesses are perpendicular anisotropy, and in addition to the value of the coercive field increases with Nb thickness, squareness and anisotropic magnetic field is extremely stable, Nb infer the structure changes in the thickness of the perpendicular anisotropy has little effect. In full structures, perpendicular magnetic anisotropy weredecreases when thickness increases. Nb = 1.0nm, 1.5nm, m1 and m2 trends are consistent with results showing both the upper and lower CoFeB layers produce magnetic dead CoFeB layer is very similar. Nb = 2.0nm, annealing temperature in between 255oC and 345oC, m1 increase with temperature increase, but m2 decrease as temperature increase, as shown in the hysteresis curve of this annealing temperature is different to Nb = 1.0 and 1.5nm. Our experimental data are compared with the reference literature, we found that coupling energy, anisotropy energy and annealing temperature value to Nb as spacer layer synthetic antiferromagnetic structure are lower than with Ru as the spacer layer synthetic antiferromagnetic structure .

目錄

封面內頁
簽名頁
中文摘要．．．．．．．．．．．．．．．．．．．．．．．．iii
英文摘要．．．．．．．．．．．．．．．．．．．．．．．．iv
誌謝．．．．．．．．．．．．．．．．．．．．．．．．．．v
目錄．．．．．．．．．．．．．．．．．．．．．．．．．．vi
圖目錄．．．．．．．．．．．．．．．．．．．．．．．．．viii
表目錄．．．．．．．．．．．．．．．．．．．．．．．．．x

第一章　緒論．．．．．．．．．．．．．．．．．．．．．． 1
第二章　理論基礎．．．．．．．．．．．．．．．．．．．．2
2.1垂直異向性(Perpendicular Magnetic Anisotropy, PMA)．．．．．．．．．．． ．．．．．．．．．．2
2.2 反鐵磁耦合．．．．．．．．．．．．．．．． ．5
2.3 Spin-Flip and Spin-Flop Transition．．．．．． 6
第三章 實驗儀器與實驗步驟
3.1 濺鍍系統．．．．．．．．．．．．．．．．．． 11
3.1.1 濺鍍原理．．．．．．．．．．．．．．．．． 12
3.2 振動樣品磁性分析儀．．．．．．．．．．．．．13
3.3 熱退火系統．．．．．．．．．．．．．．．．．14
3.4 實驗步驟．．．．．．．．．．．．．．．．．．15
第四章 實驗結果與討論
4.1 MgO/CoFeB(x)/Nb上結構磁性量測．．．．．．．． 17
4.2 Nb(x)/CoFeB/MgO 下結構磁性量測．．．．．．． 22
4.3 MgO/CoFeB/Nb(x)/CoFeB/MgO全結構磁性量測．．27
第五章 結論．．．．．．．．．．．．．．．．．．．．．．37
參考文獻．．．．．．．．．．．．．．．．．．．．．．．．39

圖目錄

圖2.1.1 異向性常數與磁性層厚度與厚度關係示意圖．．．．．3
圖2.2.1 人工反鐵磁結構圖．．．．．．．．．．．．．．．．5
圖2.3.1 Co/Cu(x)/Co 成長於(110)基板上和(111)基板上之磁滯曲線．．．．．．．．．．．．．．．．．．．．．．．．．．．7
圖2.3.2 spin-flop transition 示意圖．．．．．．．．．．．．．8
圖2.3.3 反鐵磁耦合磁滯曲線形貌．．．．．．．．．．．．．9
圖2.3.4 spin-flip與spin-flop磁矩翻轉示意圖．．．．．．．．10
圖3.1.1 Sputter 儀器圖．．．．．．．．．．．．．．．．．11
圖3.2.1 VSM裝置示意圖．．．．．．．．．．．．．．．．13
圖3.4.1 實驗流程示意圖．．．．．．．．．．．．．．．． 15
圖4.1.1 上結構Ta/MgO/CoFeB(x)/Nb．．．．．．．．．．．17
圖4.1.2 Ta/MgO/CoFeB(x)/Nb未退火之磁滯曲線圖．．．．．18
圖4.1.3 Ta/MgO/CoFeB(x)/Nb退火之磁滯曲線圖．．．．．．19
圖4.1.4 上結構的(a)飽和磁化量和殘餘磁化量、(b)矯頑場、(c)磁異向場．．．．．．．．．．．．．．．．．．．．．．．．．21
圖4.2.1 下結構Nb(x)/CoFeB/MgO/Ta．．．．．．．．．．．22
圖4.2.2 Nb(x)/CoFeB/MgO/Ta未退火之磁滯曲線圖．．．．．23
圖4.2.3 Nb(x)/CoFeB/MgO/Ta退火之磁滯曲線圖．．．．．．24
圖4.2.4 下結構的(a)飽和磁化量和殘餘磁化量、(b)矯頑場、(c)磁異向場．．．．．．．．．．．．．．．．．．．．．．．．．25
圖4.2.5 Nb(x)/CoFeB/MgO/Ta退火之磁異向能．．．．．．．26
圖4.3.1 全結構Ta/MgO/CoFeB/Nb(X)/CoFeB/MgO/Ta．．．．27
圖4.3.2 Ta/MgO/CoFeB/Nb(1.0)/CoFeB/MgO/Ta 退火M-H圖
．．．．．．．．．．．．．．．．．．．．．．．．．．．．29
圖4.3.3 Ta/MgO/CoFeB/Nb(1.5)/CoFeB/MgO/Ta 退火M-H圖
．．．．．．．．．．．．．．．．．．．．．．．．．．．．30
圖4.3.4 Ta/MgO/CoFeB/Nb(2.0)/CoFeB/MgO/Ta 退火M-H圖
．．．．．．．．．．．．．．．．．．．．．．．．．．．．31
圖4.3.5 退火溫度與單一層磁化量之關係．．．．．．．．．．34
圖4.3.6 退火溫度與飽和磁化量及殘餘磁化量之關係．．．．．35
圖4.3.7 參考文獻[10]上圖:退火溫度與飽和磁化量及殘餘磁化量之關係。下圖:退火溫度與單一層磁化量之關係．．．．．．．． 36

表目錄

表4.1.1 退火後飽和磁化量、殘餘磁化量、矯頑場、方正性及磁異向場比較．．．．．．．．．．．．．．．．．．．．．．．21
表4.2.1 退火後飽和磁化量、殘餘磁化量、矯頑場、方正性及磁異向場比較．．．．．．．．．．．．．．．．．．．．．．．26
表4.3.1 Ta/MgO/CoFeB/Nb(x)/CoFeB/MgO/Ta 耦合能J
．．．．．．．．．．．．．．．．．．．．．．．．．．．．32
表4.3.2 Ta/MgO/CoFeB/Nb(x)/CoFeB/MgO/Ta 磁異向能K
．．．．．．．．．．．．．．．．．．．．．．．．．．．．32

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