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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/23249
標題: | 鐵在鎳鋁(001)與在部份覆蓋氧化鋁的鎳鋁合金(001)
之磁性研究 Magnetic Properties of Fe on NiAl(001) and on Patterned Alumina/NiAl(001) |
作者: | Wei-Shu Li 李瑋舒 |
指導教授: | 林敏聰 |
關鍵字: | 磁奈米顆粒, magnetic nanoparticles, |
出版年 : | 2009 |
學位: | 碩士 |
摘要: | 隨著磁記錄密度不斷增加和奈米磁顆粒的重要性與日俱增,微米尺度磁區間的交互作用也漸漸被大家所注意。鎳鋁在高溫曝氧會形成單晶結構的氧化鋁,經由巧妙曝氧量的控制可以掌控氧化鋁的覆蓋比例與未被氧化鋁覆蓋的鎳鋁區塊的大小。這樣的樣品經過鐵的覆蓋會在氧化鋁上形成奈米顆粒排列,而在未被氧化鋁覆蓋的鎳鋁區塊上可以形成膜狀結構。選擇適當的鐵覆蓋厚度可以同時使奈米鐵顆粒呈現順磁性而鐵膜呈現鐵磁性。因此我們順利地利用自組方式隔出一區區的磁區塊,而且可以藉由調整曝氧量的多寡調整這些磁區塊的間隔與大小。利用掃描穿遂顯微鏡得知隨著曝氧量增加每個磁區面積變小、不同磁區間距離變大和磁區數目變多。利用磁光柯爾效應研究磁滯曲線的方形程度了解到較多的曝氧量會減弱磁區間的有序排列能力。當增加鐵覆蓋厚度使鐵奈米顆粒與鐵薄膜均呈現鐵磁性發現鐵磁性奈米顆粒的磁交互作用強度不及鐵的薄膜。磁矩相對於厚度的關係在鐵覆蓋在圖樣化氧化鋁/鎳鋁(001)與鐵覆蓋在純鎳鋁(001)有不同的分佈趨勢,藉此可以驗證鐵奈米粒子的磁性特徵。此外鐵在這兩類的樣品上都有自旋方向轉向(SRT)的現象,隨著厚度的增加垂直分量均會隨之消失。另外鐵在純鎳鋁(001)上展現出二層臺階狀的磁滯曲線,這也許暗示鐵在鎳鋁的樣品有四軸夾雜著二軸對稱的異向軸。 Following with the density of magnetic recording and the importance of nanoparticles increase, the interaction between sub-micron domains receives much attention. Exposing oxygen on NiAl(001) at high temperature results in single crystalline alumina. By controlling the amounts of oxygen dosage we could obtain different area ratio of alumina coverage over uncovered NiAl(001). Fe atoms deposited on such sample have two growth modes. Fe on uncovered NiAl grows as film, but Fe on Al2O3 stripes grows as nanoparticles. Choosing appropriate Fe coverage , we could make the ferromagnetic Fe films separated by paramagnetic Fe nanoparticles. Using this method we successfully obtain Fe domains. And by controlling the amounts of oxygen dosage we can get different domain sizes. Utilizing STM we fund at higher oxygen dosage the area of single Fe film becomes smaller, the separation between two Fe films becomes larger, and the number of Fe films becomes larger. Utilizing MOKE we find at higher oxygen dosage the squareness of hysteresis loop becomes smaller. That implies higher oxygen dosage degrades the order coupling. When increasing the Fe coverage, the strength of exchange coupling in ferromagnetic nanoparticles is weaker than ferromagnetic films. Besides, Fe on patterned alumina/NiAl(001) and Fe on pure NiAl(001) all reveal SRT(spin reorientation transition) phenomena, and at higher Fe coverage the perpendicular component of magnetization disappeared. And higher Fe coverage on pure NiAl expresses two steps hysteresis loops, that might imply the cubic easy axes are mixed with a uniaxial axis. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/23249 |
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顯示於系所單位: | 物理學系 |
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