奈米鑄型軟磁薄膜之磁化過程研究

Magnetization Processes of Patterned Permalloy Nanostructures

賴梅鳳(Mei-Feng Lai)

指導教授 ： 張慶瑞

國立臺灣大學/理學院/物理研究所/博士(2005年)

https://doi.org/10.6342/NTU.2005.10065

摘要

摘要

本論文中我們藉由微磁學模擬以及實驗的方法，研究了具有幾何高度對稱及邊界平滑特性的橢圓以及環形兩種鑄形軟磁薄膜之磁化態及各種磁化過程。首先我們將對本研究的理論背景作一個簡單的介紹，接著我們將介紹各種磁化態以及一些特殊的磁化態在外場下的變化。
我們從模擬與實驗中證實了平面皺褶模式的存在，並且可以在翻轉前的一小段場距觀察到磁化呈現穩定的波狀結構，而此種穩定的結構跟邊界條件有很大的關係。我們接著更進一步找出藉由此種皺褶介入模式的磁化翻轉，以及藉由磁化渦漩傳播介入模式的磁化翻轉在翻轉機制相圖中各自存在的區域與界線。此外，在這兩種模式的交界區域，我們還發現了一種具有極大翻轉場的混和模式。
在環狀薄膜研究方面，我們發現環狀薄膜具有三種穩定態， 並且在磁化曲線上呈現三階段的翻轉模式及其對應的跳躍。我們發現其在磁阻量測上，磁疇壁被電極覆蓋所造成的短路效應，將會使得磁阻的樣貌呈現截然不同的表現。此外，我們亦利用磁阻量測的方法來定出磁性環狀薄膜的兩種翻轉場。我們發現與磁疇成核有關的翻轉場將隨著薄膜平面尺寸的減小或是薄膜厚度的變大而增加，但與磁疇壁去釘扎效應有關的翻轉場則沒有明顯的改變趨勢。

關鍵字

鑄型 ； 薄膜 ； 磁化 ； 奈米

並列摘要

Abstract
In this thesis we use micromagnetic simulation and experimental method to investigate the magnetization states and magnetization processes of elliptical and ring-shaped patterned thin films that have highly symmetric geometries and smooth boundaries. First we will give a brief introduction to the theoretical background of our research. Various magnetization states and the field-evolution of some states will be described.
From the simulation and experiment the existence of planar buckling mode is demonstrated. Stable magnetization waving structures can be observed within a small field interval before switching. The stable magnetization waving structures are closely related with the boundary condition of the magnetic thin film. Respective regions of the switching mechanism phase diagram is further derived for such buckling-involved reversal mode and vortex-propagation-involved reversal mode. Besides, in the phase boundary we also find a mixed mode of the above two reversal modes, and this reversal mode corresponds to very large switching field.
In the research on ring-shaped magnetic thin films, we find that there exist three stable states that lead to an unconventional triple-switching characteristic. Using magnetoresistance measurement we find that the short circuit effect caused by the patched leads on the magnetic domain walls strongly influences the magnetoresistance characteristic. Besides, magnetoresistance measurement is also used to determine the switching fields of the ring-shaped magnetic thin films. We find that the switching field related with the domain nucleation increases with decreasing of lateral size or with increasing of thickness, and the switching field related with the domain-wall depinning does not have significant lateral-size and thickness dependences.

並列關鍵字

magnetization ； patterned ； thin film ； nano

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