自旋量子井對交換偏耦合的影響

Study of exchange bias couping through spin-polarized quantum well

莊程豪(Cheng-Hao Chuang)

指導教授 ： 林敏聰

國立臺灣大學/理學院/物理研究所/碩士(2003年)

https://doi.org/10.6342/NTU.2003.00017

摘要

為了了解透過非磁性金屬層中的量子干涉效應對於磁性交換偏耦合所產生
的影響，本實驗先在銅(001)上鍍上鐵錳合金反鐵磁層，再鍍上鈷的鐵磁層，而後在樣品上面隨著 Z 軸來做銅的階梯式薄膜(Cu;Co;FeMn;Cu(001)) 。在超高真空腔中，利用分子磊晶 (Molecular Beam Evaporation, MBE) 技術來穩定且均勻鍍膜，在此同時利用中能電子繞射 (Medium Election Energy Diffraction, MEED) 來即時監控膜的層數與生長模式，並使用歐傑電子能譜儀 (Auger Election Spectroscopy, AES)來確定薄膜的厚度以及其成分比例﹔至於薄膜結構方面，我們利用低能電子繞射 (Low Election Energy Diffraction, LEED) 來分析薄膜的表面結構，並利用磁光柯爾效應(Magnetic-Optic Kerr Effect, MOKE)
來觀察超薄膜的磁性特性。經由一系列有系統的研究後，我們發現誚b最上層的銅對於16ML Co;20ML FeMn;Cu(001) 的系統中的磁性特性有很劇烈的影響。隨著銅厚度(t_[Cu[) 的改變，系統中的交換偏耦合(Exchange Bias) ，矯頑力(Covercivity) ，磁化量 (Magnetization)都有很明顯的改變。依據不同的磁性性質，我們將銅的影響可分成五區，第一區為
t_[Cu]=0ML ，其主要是觀察鐵磁與反鐵磁層界面上磁性偏耦合現象，第二區為t_[Cu]<1ML 表面上銅開始引起磁性性質變化，第三區為1ML

關鍵字

交換偏耦合 ； 反鐵磁性 ； 鐵磁性 ； 磁光科爾效應 ； 量子井

並列摘要

To realize the relation of quantum interference in the space layers between vacuum and Co/FeMn bilayers, it was observed by magneto-optic kerr effect (MOKE). FeMn alloy was first deposited on Cu(001) to serve as the antiferromagnetic substrate. Co layers were used as the ferromagnet to study
applications of exchange bias. Cu wedge was deposited on the top of Co/FeMn/Cu(001) by moving the substrate behind a knife-edge shutter.
The sample was prepared by molecular beam evaporation (MBE) method, deposited on Cu(001). Composition and film thickness were calibrated by oscillations of the medium energy electron diffraction (MEED), and cross checked by Auger electron spectroscopy (AES). All grown modes were accompanied by clear
intensity oscillations in medium energy electron diffraction , indicating Frank der Merve growth in a layer by layer fashion. On the other hand, low energy electron diffraction (LEED) and I/V LEED curves were used to measure film structure. The focus laser was used to measure magneto-optics Kerr effect (MOKE), which gives us excellent resolution of the thickness dependence.
We presented a systematic study of the exchange bias and coercivity as a function of the Cu layers thickness in the Cu(wedge)/Co/FeMn/Cu(001). The coercive field displayed five times than original magnitude, when Cu thickness overcomes approximate 3ML. When Cu thickness over 3ML, coercive field stayed about 280 Oe. Until Cu thickness over 5ML, coercive field
increased continuously. In the wide range, the oscillation of exchange bias in Cu/Co/FeMn/Cu(001) was 4-5ML.

並列關鍵字

magnetic kerr effect ； antiferromagnetic ； exchange bias ； quantum well ； ferromagnetic

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