Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/10091
標題: Microstructures and Magnetic Properties of Ferromagnetic/Antiferromagnetic Thin Films
鐵磁/反鐵磁薄膜微結構及磁性質之研究
作者: Ting, Yi-Wen
丁怡文
關鍵字: exchange bias;交換偏壓
出版社: 材料科學與工程學系所
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摘要: 
Composite films of (i) Ni80Fe20/CoO, Ni80Fe20/CoO/Co and (ii) [NiFe/Mn(Cr)]50 were prepared by dual ion-beam deposition technique. The structural and magnetic properties of these composite films were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM), and superconducting qutantum interferemce device (SQOID) magetometry down to 5K.
(i) XRD results have shown that the top Ni80Fe20 layer consisted of a rock-salt (a~3.55 Å) and the intermediary CoO layer exhibited a f.c.c. CoO phase (a~4.28 Å), whereas the bottom Co layer consisted of a h.c.p. Co phase in Ni80Fe20/CoO/Co trilayer system. The Ni80Fe20 and CoO layer of Ni80Fe20/CoO bilayer system exhibited the same structures as Ni80Fe20/CoO/Co trilayer system. TEM results have shown that the grain sizes of these polycrystalline composite films range from 5 nm to 15 nm. Magnetometry results at 5K indicate that the exchange bias field (Hex~ −38 Oe) is the largest in NiFe/CoO bilayer when CoO thickness was 128 nm. In trilayer system, it was found that the largest negative exchange bias field (Hex~-24.9 Oe) appearance when CoO thickness was 128 nm.
(ii) Both stucture of [Ni80Fe20/Mn]50 and [Ni80Fe20/Cr]50 multilayers are f.c.c. Ni80Fe20 (a~3.55Å) phase; moreover, the former shows the b.c.c. Mn (a~8.91Å) and the latter is b.c.c. Cr (a~2.90 Å) phase, respectively, confirmed by TEM diffraction pattern. The grain sizes of these polycrystalline composite films are from 2 nm to 15 nm confirmed by dark filed images. Magnetometry results at 5K indicate that the exchange bias field of [Ni80Fe20/Mn]50 and [Ni80Fe20/Cr]50 multilayers system is enhanced by ion beam bombardment.

本研究主要分為兩大部分,利用雙離子束濺鍍系統製備(i)鎳鐵/氧化鈷(Ni80Fe20/CoO)及鎳鐵/氧化鈷/鈷(Ni80Fe20/CoO/Co)並且改變其反鐵磁層厚度,探討反鐵磁層厚度以及雙鐵磁層對磁性質之影響;(ii) 鎳鐵/錳及鎳鐵/鉻多層膜系統中,在鍍膜過程中,利用不同電壓(0~150V)之輔助離子束(End-Hall)來轟擊薄膜,探討經轟擊過後鐵磁層與反鐵磁層交換偶合現象的關係。
鎳鐵/氧化鈷雙層薄膜是由面心立方(f.c.c.)結構的鎳鐵(晶格常數= 3.55Å)與面心立方結構的氧化鈷(晶格常數= 4.28Å)所組成,晶粒大小介於5~15nm之間。磁性分析結果顯示在5K、20kOe場冷下鎳鐵/氧化鈷雙層薄膜在厚度為128 nm處有最大的交換偏壓場(Hex~-38Oe),實驗結果顯示交換偏壓隨著反鐵磁層厚度的增加有上升後下降的趨勢。
鎳鐵/氧化鈷/鈷三層薄膜是由面心立方結構的鎳鐵與面心立方結構的氧化鈷及六方最密堆積(h.c.p.)的鈷(晶格常數a=2.52 Å , c=4.10Å)所組成,晶粒大小介於5~15nm之間。磁性分析結果,在5K、20kOe場冷下氧化鈷厚度為128 nm 處同樣有最大的負交換偏壓(Hex~-24.9Oe)。結果顯示當反鐵磁層厚度的增加時交換偏壓有先升後降的情形與雙層薄膜相同。
鎳鐵/錳多層薄膜是由面心立方結構的鎳鐵與體心立方(b.c.c.)結構的α-錳(晶格常數= 8.91Å)所組成,晶粒大小介於2~15nm之間。磁性分析結果顯示在5K、20kOe場冷下交換偏壓由+132Oe(VEH=0V)上升至+162 Oe(VEH=150V) ,顯示離子束轟擊會造成交換偏壓的上升。
鎳鐵/鉻多層薄膜是由面心立方結構的鎳鐵與體心立方結構的鉻(晶格常數= 2.90Å)所組成。晶粒大小範圍都落在2~15nm之間。在5K、20kOe場冷後實驗結果發現經過離子束轟擊之試片其交換偏壓較大,由-0.5 Oe(VEH=0V)到-104 Oe(VEH=150V)。特別的是,離子束轟擊會造成鎳鐵居里溫度的改變,使鎳鐵的居里溫度介於160 K與298 K之間。
URI: http://hdl.handle.net/11455/10091
其他識別: U0005-0306201116404100
Appears in Collections:材料科學與工程學系

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