近年來將奈米磁性材料應用在數位磁性儲存裝置是提昇儲存容量的一種新趨勢，其中鈷銅磁性奈米粒子是具有應用潛力的磁性材料之一。因此，若能深入探討鈷銅奈米粒子的材料性質，將能作為未來在數位磁性儲存元件應用與發展的重要參考。本文以鈷銅奈米合金的修正型Tight-Binding勢能，利用分子動力學理論模擬鈷銅奈米粒子在退火過程中的結構變化，藉由徑向分佈函數（RDF）、角度關連函數（ACF）與平均鍵長統計，探討在較高與較低的鈷濃度比例條件下，對其結構排列的影響，並從中求取鈷原子在鈷銅奈米粒子中的分佈函數。本研究再以兩種計算稀釋合金磁性的方法─RKKY間接交互作用理論與量子微擾理論， 與分子動力學計算的鈷原子分佈函數結合，計算鈷銅奈米粒子在不同比例條件下，磁性對應溫度的分佈變化，並預測其居禮溫度。

The Co-Cu nanoparticles is one of the magnetic materials that have considerable potential for a variety of industrial applications, including giant magnetoresistance (GMR) digital storage devices and have therefore attracted a great deal of attention in recent years. For this reason, it will be an important reference to the development of the magnetic digital storage devices if we can go deep into study the material properties of the Co-Cu nanoparticles.
This study uses molecular dynamics simulations to investigate the crystalline process of Co-Cu nanoparticles of high and low Co concentrations (5~25 %) during the annealing process. The modified many-body tight binding potential is adopted to accurately model the Cu-Cu, Co-Co, and Co-Cu pair inter-atomic interactions. The structural transformations at the upper and lower melting points are observed by the radial distribution function (RDF), the angle correction function (ACF) and the average bond lengths. finally, we employs molecular dynamics simulations to predict the distribution function of diluted magnetic Co atoms in a Cu host and then uses the the Ruderman-Kittel-Kasuya-Yosida (RKKY) theory and quantum magnetism theory to calculate the magnetic properties of the Co-Cu alloys at different temperature, including their Curie temperature.

目錄
第1章 緒論 1
1.1 研究動機 2
1.2 文獻回顧 5
1.3 本文架構 9
第2章 分子動力學理論 10
2.1 勢能函數 11
Tight-binding勢能 12
2.2 運動方程 15
2.2.1 Velocity Verlet algorithms 15
2.3 徑向分佈函數 (RADIAL DISTRIBUTION FUNCTION, RDF) 17
2.4 角度關聯函數 (ANGULAR CORRELATION FUNCTION, ACF) 19
2.5 分子動力學數值模擬方法 20
2.5.1 Verlet List表列法 21
2.5.2 Cell Link表列法 22
2.5.3 Verlet List表列法結合Cell Link表列法 23
2.6 無因次化 24
第3章 分子動力學與磁性理論的結合 26
3.1 鈷銅奈米粒子物理模型的建構 27
3.2 RKKY間接交互作用理論 30
3.3 量子微擾理論 33
第4章 結果分析與討論 37
4.1 鈷銅奈米粒子微結構變化的討論 38
4.2 RKKY磁性計算結果的討論 48
4.3 量子磁性計算結果的討論 51
第5章 結論與建議 53
5.1 結論 54
5.2 建議與未來展望 55

表目錄
表 2.1鈷銅原子間之TIGHT-BINDING勢能參數 14
表 2.2無因次化基準量 25
表 2.3各物理量之無因次化量 25

圖目錄
圖 2.1 二體勢能示意圖 11
圖 2.2 多體勢能示意圖 12
圖 2.3 VELOCITY VERLET演算法流程圖 16
圖 2.6 截斷半徑示意圖 20
圖 2.7 VERLET LIST示意圖 21
圖 2.8 CELL LINK示意圖 22
圖 2.9 VERLET LIST 結合 CELL LINK建立鄰近表列 23
圖 3.1(A)完美F.C.C.晶格排列的鈷銅奈米粒子初始模型，總原子數為9597顆。(B)在2000K高溫退火處理下，平衡後的形貌，深色粒子為鈷原子，淺色粒子為銅原子。(C)退火完成後，在3K低溫下的鈷銅奈米粒子形貌，濃度比例為5％。(D) 退火完成後，在3K低溫下的鈷銅奈米粒子形貌，濃度比例為25％。 28
圖 3.2分子動力學電腦模擬流程圖 29
圖 4.1鈷銅奈米粒子退火過程中之能量曲線對應溫度分佈圖。虛線部分為鈷原子濃度X=5%，其上熔點為910K，下熔點為810K;實線部分為鈷原子濃度X=25%，其上熔點為1260K，下熔點為1140K。 42
圖 4.2(A)是鈷原子濃度比例為5%(B)是鈷原子濃度比例為25%的上、下熔點與其中間溫度所對應的RDF分佈圖。 43
圖 4.3(A)是鈷原子濃度X=5%(B)是鈷原子濃度X=25%的鈷銅奈米粒子，在上、下熔點的CO-CO、CU-CU與CO-CU分開統計的RDF分佈圖。 44
圖 4.4(A)是鈷原子濃度X=5%(B)是鈷原子濃度X=25%的鈷銅奈米粒子，在上、下熔點的角度關連函數(ACF)變化曲線圖。 45
圖 4.5是鈷原子濃度X=5%與25%的CU-CU、CO-CO與CO-CU鍵長在不同溫度下的變化分佈圖。 46
圖 4.6是鈷原子濃度X= 25%的CU-CU、CO-CO與CU-CO之 RDF第一個尖峰值對應其溫度變化統計圖。 47
圖 4.7是鈷銅奈米粒子在五個濃度比例5%、10%、15%、20%、25%條件下，其鈷原子的分佈函數G(R)圖。(A)是1600K，(B)是300K。 49
圖 4.8是五個鈷原子濃度的奈米粒子在不同溫度下的磁性強度變化圖，小插圖是鈷原子濃度與其居禮溫度的對應關係。 50
圖 4.9分別是25％與40％的鈷銅奈米粒子在無外加磁場條件下，其磁化強度對應溫度的變化關係圖。 52

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