在此論文中, 我們對不同濃度的磁性流體薄膜之有序結構做一系統性之研究. 不僅建立了有序結構之形成因子, 更在理論上提出模型來解釋此有序結構之形成機制. 我們觀察磁性流體薄膜在外加鉛直及平行磁場下所形成之結構時. 發現在外加平行磁場下, 磁性流體形成週期性有序鏈狀結構. 而在外加鉛直磁場下, 低磁場時觀察到有序六角結構; 高磁場下卻轉為迷宮結構. 因此, 我們提出當磁場增加時, 有一相變存在於磁性流體薄膜中.此外, 實驗中並發現此有序六角結構及其形成過程均與磁場增加率dH/dt相關聯. 為了澄清有序結構之機制, 我們提出數個模型來解釋鉛直磁場下, 圓柱間距與外加磁場之關係, 並與實驗結果相比較. 結果顯示圓柱偶極模型與實驗結果最契合, 此意謂圓柱尺寸所造成之效果不能被忽略. 我們亦研究了含許多微滴之過飽和磁性流體薄膜之有序結構. 發現當外加鉛直磁場增加時, 偶極間之作用力促使這些微滴分枝並斷裂, 最後形成六角結構. 此一新的相變是之前從未發現的. 為了檢驗有序結構於一維及二維間之轉變, 我們亦研究傾斜磁場下, 磁性流體薄膜磁結構之變化. 發現當增加磁場傾斜角時, 此六角結構漸漸轉為週期性的長鏈結構.而此長鏈結構之間距超過臨界角時突然增加, 因此推測當傾斜角增加時有一轉變發生於此系統中.

The ordered structures of the magnetic fluid thin film for the diluted, saturated, and over-saturated magnetic fluid have been studied systematically.The forming factors and the model explaining of the ordered structures were also established to understand the mechanisms of the ordered structures. The quasiperiodic chains in a parallel magnetic field, the perfect hexagonal crystal structure in a weaker perpendicular field, and the labyrinthine patternin a stronger perpendicular field were observed. It was suggested that the phase transitions exist in the ferrofluid film system as the field strength increases. And also, the forming process of the columns and ordered structres under magnetic fields for ferrofluid films were found to be dependent of the sweep rate of the magnetic field dH/dt. To clarify the mechanisms of the ordered structure, models explaining the relationship between the column distance of magnetic fluid thin films under perpendicular magnetic fields are studied. The theoretical results calculated based on these models are compared with those obtained from experiments. It reveals that the finite size effects of the column diameter and the column length can not be ignored and the column-dipole model is the best simulating the actual situation. The ordered structures for the over-saturated magnetic fluid were also examined and the pattern formations of magnetic fluid films containing magnetic microdrops under applied perpendicular magnetic fields were investigated. At higher magnetic fields, the connectivity of drops broke up in which the dipole interaction becomes dominated; and an equilibrium hexagonal structure formed inside the film finally. A new phase transition exists between the labyrinthine structure and the hexagonal structure, which has not been seen before. To check the transition between the 1-D and 2-D ordered structure, the patterns of the magnetic structure under tilted magnetic fields were taken. As tilted angle theta exceeding a critical value, the tilted segments with a hexagonal structure began to form longer periodic chains with an abrupt increasing of d. Hence, a transition from the magnetic hexagonal structure to a periodic chain structure at theta_c existed for magnetic fluid thin film.