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研究生: 蕭詠銜
Yeong-Shyan Hsiao
論文名稱: 鎳奈米微粒間交互作用對磁特性的影響
指導教授: 李文献
Wen-Hsien Li
口試委員:
學位類別: 碩士
Master
系所名稱: 理學院 - 物理學系
Department of Physics
畢業學年度: 95
語文別: 中文
論文頁數: 83
中文關鍵詞: 奈米微粒
外文關鍵詞: nanoparticle, magnetic, Ni
相關次數: 點閱:9下載:0
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  • 本實驗利用熱蒸鍍法製作鎳奈米微粒,並藉由對樣品壓合的方式來調控微粒間的間距,以觀察微粒間交互作用對磁特性的影響。
    自然聚合的鎳奈米微粒在外加磁場200 Oe時blocking temperature為200 K,並觀察到在4.5 K至300 K的溫度範圍內皆無磁滯現象。外加磁場0.15 T時自然聚合的鎳奈米微粒約在50 K有一反鐡磁性現象的轉折點,聚合密度增加,微粒間作用力增強,反鐡磁性的轉折點溫度愈高,且在此轉折點溫度以上無磁滯現象,以下有磁滯現象,顯示在轉折溫度以下因微粒間交互作用力較熱擾動大而顯現出來。此外亦發現經過壓合的樣品,其磁滯曲線並未對零場對稱,偏移的程度隨壓合密度增加而增大,在壓合密度達到60 %時偏移達到最大值約400Oe,此偏移可能為奈米鎳粒子表面效應所造成的自旋玻璃態。當外加磁場回到零點時,這些表面的磁矩排列的方向仍然維持在原外加磁場方向,因此奈米鎳微粒中鐵磁核心的部份仍然可以感受到這些來自表面磁矩所造成的磁場影響,而使磁滯偏移。此偏移量隨壓合密度增加而增加意味著表面的這層自旋玻層的厚度隨著壓力增加而變大,各個不同壓力的飽和磁矩隨著壓力增加而減少,壓合密度達60 %時,樣品的飽和磁矩僅剩下塊材的50 %。


    Ni nanoparticles were fabricated by the thermal evaporation method. We control the distance among particles by pressing the loosely packed nanoparticle powder samples, and studying the influence of interparticle interaction on the magnetic characters of Ni nanoparticle.
    The blocking temperature of the loosely packed Ni nanoparticle powder sample in applied magnetic field 200 Oe is 200 K, we observe that there is not hysteresis at temperature range 4 K to 300 K. And at applied magnetic field 0.15 T, there is an antiferromagnetic transition at 50 K. The interaction among nanoparticles increases when the compacting density increases. The temperature of antiferromagnetic transition also increases, and there is not hysteresis above the antiferromagnetic transition temperature. Hysteresis is observed below the transition temperature. It means interaction of particles is lager than thermal energy below the transition temperature. Beside, we also observe the hysteresis curve is not symmetry at zero field in compacted samples. When compacting density increases, shift of hysteresis is increases. Compacting density is 60 %, the shift is about 400 Oe. This shift may form by spin glass of surface effect of Ni nanoparticles. As applied magnetic field gets back to zero field, the direction of surface magnetic moment is ordered by original applied magnetic field direction. Ferromagnetic central part of nickel nanoparticles can experience these come from surface magnetic moment effect, and make the hysteresis shift. The shift increases as compacting density increases, it means that surface spin glass layer become heavy as the pressure increases, and saturation magnetism of each different pressure reduces as the pressure increases. While compacting density is 60 %, the saturation magnetism of sample only 50 % of bulk left.

    論文摘要.................................................. Ⅰ Abstract.................................................. Ⅱ 致謝...................................................... Ⅲ 目錄...................................................... Ⅳ 圖目...................................................... Ⅶ 表目...................................................... Ⅹ 第一章 簡介 1-1 奈米材料的特性...................................... 1 1-2 磁性種類簡介........................................ 4 1-3 塊材鎳的基本特性.................................... 7 參考資料............................................ 8 第二章 樣品備製與實驗儀器 2-1 奈米壓合材料的製備.................................. 9 2-2 X光繞射儀裝置...................................... 13 2-3 磁化強度實驗的原理與裝置........................... 15 參考資料........................................... 18 第三章 奈米微粒的磁特性 3-1 磁滯曲線........................................... 19 3-2 超順磁性........................................... 21 3-3 連季寧方程式....................................... 25 3-4 聚合密度與微粒間距................................. 27 (1)樣品密度與施加壓力的關係.......................... 27 (2)微粒間距探討...................................... 28 參考資料........................................... 33 第四章 鎳奈米微粒磁特性 4-1 X光繞射譜圖分析.................................... 34 4-2 鎳奈米微粒的磁性特性............................... 41 參考資料........................................... 49 第五章 微粒交互作用對磁性的影響 5-1 聚合密度對反鐡磁特性溫度的影響..................... 50 5-2 聚合密度對磁滯的影響............................... 53 5-3 磁滯分析........................................... 58 (1)聚合密度對表層無序態厚度影響...................... 58 (2)聚合密度對磁矩的影響.............................. 62 (3)聚合密度對磁滯對稱性的影響........................ 66 參考資料........................................... 69 第六章 結論............................................. 70

    第一章
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    第二章
    [1]羅吉宗、戴明鳳、林鴻明、鄭振宗、蘇程裕、吳育民著,奈米科技導論,全華科技圖書股份有限公司
    [2]許樹恩、吳泰伯著,X光繞射原理與材料結構分析,國科會精儀中心 (1993)
    第三章
    [1]Soshin Chikazumi著,張煦、李學養合譯,磁性物理學(1964)
    [2]Stephen Blundell, Magnetism in Condensed Matter, P.170(2003)
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    [7]B.D. Cullity, Introduction to Magnetic Materials(University of Notre Dame), P.412(1984)
    第四章
    [1]許樹恩、吳泰伯著,X光繞射原理與材料結構分析,國科會精儀中心 (1993)
    [2]C. Kittel, Introduction to Solid State Physics, 7th. edition (Willy, NewYork, 1996), P.443
    [3]J. M. D. Coey, Physical Review Latters, volume27, number 17 (1971)
    [4]Xavier Batlle and Amilcar Labarta, Journal of Physics D: Applied Physics, 35 R15-R42 (2002)
    [5]D. K. Kin et Al., Journal of Magnetism and Magnetic Materials, 225, P.256-P.261(2001)
    [6]B.D. Cullity, Introduction to Magnetic Materials(University of Notre Dame)(1984)
    第五章
    [1]J. Dai, J. Q. Wang, C.Sangregorio, J. Appl. Phy. 87, 10(2000)
    [2]F. C. Fonseca, G. F. Goya, R. F. Jardim, Phy. Rev. B, 66, 104406(2002)
    [3]H. Wang, T. Zhu, K. Zhao, Phy. Rev. B, 70, 092409(2004)
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    [5]Xavier Batlle and Amilcar Labarta, J. Phys. D:Appl. Phys. 35 R15-R42(2002)

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