Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/11509
標題: 鎳鐵/氧化鈷/鈷及離子束轟擊鎳鐵/氧化鐵薄膜之微結構及磁性質研究
The microstructural and magnetic characterization in NiFe/CoO/Co trilayers and ion-beam bombarded NiFe/Fe-oxide bilayers
作者: 藍天琪
Lan, Tien-Chi
關鍵字: 雙離子束濺鍍系統
Dual ion Beam Assisted Deposition
交換偏壓
Exchange Bias
出版社: 材料科學與工程學系所
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摘要: 本研究利用雙離子束濺鍍系統製備(1)鎳鐵/氧化鈷/鈷三層薄膜,探討不同氧化鈷厚度對交換偏壓效應之影響;(2)鎳鐵/氧化鐵雙層薄膜,探討離子束轟擊氧化鐵表面對鎳鐵/氧化鐵雙層薄膜之磁性質影響。 由X光繞射儀及電子顯微鏡分析顯示:鎳鐵/氧化鈷/鈷三層薄膜分別由面心立方之鎳鐵,鹽岩結構之氧化鈷及六方最密堆積之鈷所組成。磁性質研究結果顯示:在室溫下,鎳鐵/氧化鈷/鈷三層薄膜中氧化鈷厚度為5奈米,其磁滯曲線呈現台階形狀。經由場冷至10 K之鎳鐵/氧化鈷/鈷三層薄膜中,氧化鈷厚度為5奈米之樣品具有最大之矯頑磁力(Hc ~ 286 Oe),而氧化鈷厚度為12奈米之樣品具有最大之交換偏壓場(Hex ~ -143 Oe)。磁化量對溫度之相依性(零場冷及場冷)研究顯示:鎳鐵/氧化鈷/鈷三層薄膜均具有類似自旋玻璃之行為,其不同之阻隔溫度及不可逆溫度與氧化鈷厚度造成之鐵磁/反鐵磁耦合有關。此外,極化中子反射儀研究之初步結果(如:自旋非對稱與自旋翻轉機制)顯示:磁化翻轉機制隨著外加磁場改變而不同。 在離子束轟擊氧化鐵表面之鎳鐵/氧化鐵雙層薄膜結構分析(X光繞射儀、電子顯微鏡)結果顯示:鎳鐵/氧化鐵雙層薄膜均含有面心立方結構隻鎳鐵、剛玉型六方最密堆積結構之氧化鐵,並由電子能譜化學分析儀證實鎳鐵/氧化鐵雙層薄膜界面無擴散現象。磁性質分析結果顯示:室溫下,鎳鐵/氧化鐵雙層薄膜無明顯之交換偏壓。鎳鐵/氧化鐵雙層薄膜由室溫場冷到160 K時,經70 V轟擊後之樣品磁異向性降低,使矯頑磁力(Hc ~ 18 Oe)較未轟擊之樣品小。場冷至10 K下,未經離子束轟擊之鎳鐵/氧化鐵雙層膜具有最大之矯頑磁力約204 Oe,而經70 V轟擊之樣品具有最大之交換偏壓(Hex ~ -261 Oe)。最後,由磁化量對溫度之相依性結果顯示:經70 V轟擊後之鎳鐵/氧化鐵雙層薄膜具有最高之阻隔溫度(TB ~ 100 K),而未經離子束轟擊之樣品則具有最高之不可逆溫度(Tirr. ~ 250 K)。
Exchange bias (EB) is the term used to describe the unidirectional anisotropy found in a ferromagnet (FM) exchanged-coupled to an antiferromagnet (AFM). In this research, a dual ion-beam deposition technique was used to prepare the NiFe/CoO/Co trilayers with different CoO thicknesss and NiFe/Fe-oxide bilayers for ion-beam bombardment. Results have shown that the trilayer consisted of f.c.c. NiFe, roak-salt CoO, and h.c.p. Co structures. At room temperature, the NiFe/CoO/Co trilayers exhibited soft magnetic properties with coercivity close to those of reference single NiFe and Co layer, However, a step with enhanced Hc was observed in a NiFe/CoO(5 nm)/Co trilayer. The exchange bias coupling interaction between NiFe/CoO and CoO/Co was set in when field-cooling the trilayers below the Neel temperature of CoO down to 10 K. A largest exchange bias field (Hex ~ -143 Oe) resulting from competition between top and bottom FM/AFM interfaces was found in a NiFe/CoO(12 nm)/Co trilayer. In the ZFC/FC results, the NiFe/CoO/Co trilayers exhibited spin-glass-like behavior, while the different block temperature and irreversible temperature were caused by ferromagnetic/ antiferromagnetic coupling with different cobalt oxide thickness. Moreover, the preliminary PNR data were consistent with the hysteresis loop. The exchange coupling effects in NiFe/Fe-oxide bilayers consisted of f.c.c. NiFe and corundum h.c.p. α-Fe2O3 structures, there were no intermixing at ferromagnetic/ antiferromagnetic surface as characterized by Electron Spectroscopy for Chemical Analysis (ESCA). Without the exchange bias at 298 K, and after 70 V Ar ion bombarded observed decrease in Hc after field cooling (FC) to 160 K is mainly attributed to a reduced effective magnetic anisotropy. The hysteresis loops were measured parallel to the film surface after being field cooled from room temperature down to 10 K at 20 kOe. The enhanced coercivity (Hc ~ 204 Oe) for not bombarded NiFe/Fe-oxide bilayer and a maximum exchange bias (Hex ~ -261 Oe) was discovered at after 70 V bombarded. The results of ZFC/FC were discovered a largest block temperature (TB ~ 110 K) with 70 V bombarded, whereas the largest irreversible temperature (Tirr.) about 250 K observed at the NiFe/Fe-oxide bilayer at sample of not bombarded.
URI: http://hdl.handle.net/11455/11509
其他識別: U0005-2406201311101500
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-2406201311101500
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