臺灣國際科展

磁性流体薄膜在水平磁場下結構型態之研究

科展類別
臺灣國際科展
屆次
2003年
科別
物理科
學校名稱
臺北市立建國高級中學
指導老師
洪姮娥、李泗賓
作者
趙贇新
關鍵字
磁性流体薄膜,水平磁場
備註
莫斯科二○○三年科學博覽會

摘要或動機

本研究探討不同的控制變因,對磁性流體薄膜在水平磁場下有序結構的影響。我們發現,外加水平磁場於磁流體薄膜時,會形成一維有序磁鍊排列,磁鍊間距除會隨著磁場增強而變小外,另外其條件值如磁場強度、流體濃度、磁增率、薄膜寬度及厚度等也影響磁鍊間距。其中磁增率及磁流體濃度增加會使磁鍊間距變小,而凹槽寬度及薄膜厚度增加會使磁鍊間距變大等現象。至於其形成磁鍊的物理作用,我們假設薄膜有三種能量交互作用,即(1)磁鍊與外加磁場間的磁能UdH。(2)兩條同方向磁化的磁鍊間相互排斥所造成的磁能Udd。(3)熱能Uther等。藉由系統能量Udh+Udd+Uther最小化,我們導出了磁鍊間距和外加磁場之間理論上的關係,並比較實驗結果確實具有相當的一致性。因這些有序結構會引發許多的光學性質,將來這些特殊的光學性質預料應可製成可調式光柵、光開關及顯示器等光電元件,使磁流體在奈米世界及光電領域裡扮演重要角色。We investigate experimentally the structure of the magnetic chains formed in the magnetic fluid thin film under the influence of the external magnetic field parallel to the film surface. A one-dimensional ordered structure forced by magnetic chains can be obtain in the magnetic fluid film. It is worth noting that the ordered structure can be manipulated by changing the control parameters such as the magnetic field, concentration of magnetic fluid, the thickness of the film, the width of the film, and the dH/dt. On the other hand, the physical mechanism of forming the ordered structure can be also studied theoretically. These magnetic chains are regarded as magnetic dipoles and three possible interactions are condisered for the energy of the system: the attracting potential energy between the magnetic chain and H(denoted by UdH),the repulsive potential energy between two magnetic chains with parallel magnetizations(denoted by Udd), and the thermal energy Uther. The relationship between the chain distance △x and the applied magnetic field H was derived by minimizing the total energy of the system with respect to the chain distance. The experimental data is consistent with the theoretical results.


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