鐵/面心正方錳/鈷在基板銅(100)上，結合磁交換偏耦合和遠程層間磁耦合的磁性與結構研究

Abstract

本實驗內容是將Fe/fct-Mn/Co 三層結構以熱蒸鍍的方法將其鍍在銅單Cu(100)上研究此系統的磁交換偏耦合(exchange bias coupling)和遠程層間磁耦合(long range interlayer coupling)現象。 在結構方面，面心正方的鈷(fct-Co)與面心正方的錳(fct-Mn)是利用Low Energy Electron Diffraction (LEED)和I-V LEED 確定其晶格結構。在測量磁性方面，我們利用Magnetic Optical Kerr Effect (MOKE)測得一系列以不同的鐵與錳的厚度的磁滯曲線。 當fct-Mn 厚度增加至24 個原子層，Fe 和Co 的磁矩會經歷過非同調的旋轉(incoherent rotation)，造成two-step 的磁滯曲線產生。遠程層間磁耦合(long range interlayer coupling)的影響是傾向鐵和鈷的同調的旋轉(coherent rotation)。但是，Mn/Co 的磁交換偏耦合(exchange bias coupling)會增加鈷的矯頑磁力，同時也破壞到鈷跟鐵的磁矩的同調旋轉機制。結果我們發現當鐵的磁矩正在翻轉時，鈷一開始也跟隨著鐵翻轉，但是到了鐵完成180。翻轉後，鈷又會再次反轉回原始方向。 最後，我們使用磁異向能理論模型(single domain model)以模擬當磁交換偏耦合(exchange bias coupling) 和遠程層間磁耦合(long range interlayer coupling)兩者互相競爭下，所產生的上述磁翻轉機制。

In order to study the combination of exchange bias coupling and long range interlayer coupling, the Fe/fct-Mn/Co trilayers was grown on a single crystal of Cu(100). Low energy electron diffraction (LEED) and I-V LEED were used to check the crystalline structures of fct-Co and fct-Mn. We also used magnetic optical kerr effect (MOKE) to get a series of magnetic hysteresis loops with a function of Mn and Fe. When the thickness of Mn was increased to 24ML, the magnetic hysteresis loop became two-step loop with a special feature, because the Co and Fe moments underwent incoherent magnetization switching. Long range interlayer coupling preferred the coherent rotation of Fe and Co, but the exchange bias coupling of Mn/Co increased the coercivity field of Co layer, which prevented the coherent rotation. As the Fe layer flipped, the Co moment followed the Fe to rotate, and then turned back to the initial direction. Our simulation can demonstrate the phenomenon is similar to our experimental observation.