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    National Tsing Hua University Institutional Repository > 工學院  > 材料科學工程學系 > 博碩士論文  >  (001) 銥錳/鈷鐵磊晶系統中交換異向性之研究


    Please use this identifier to cite or link to this item: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/31905


    Title: (001) 銥錳/鈷鐵磊晶系統中交換異向性之研究
    Other Titles: Exchange anisotropy in epitaxial (001)IrMn/Co50Fe50 system
    Authors: 楊志彥
    Chih-Huang Lai
    Chih-Yen Yang
    教師: 賴志煌
    楊志彥
    Date: 2006
    Keywords: 交換異向性
    磁滯曲線
    磁矩翻轉
    銥錳
    鈷鐵
    磊晶
    IrMn
    CoFe
    exchange anisotropy
    double shifted loop
    hysteresis loop
    epitaxial
    Abstract: 本實驗中,我們利用直流磁控濺鍍系統將銅鍍製在經由氫氟酸浸泡過的矽基板之上,接著我們以銅為底層成功地在室溫之下成長出具有(001)磊晶結構的IrMn/CoFe鐵磁反鐵磁系統。此外,我們於鍍膜的過程中施予一外加磁場使得系統具有一單方向的磁異向性。在磁性質方面,我們發現除了在沿著加場鍍膜的方向為一個典型的具有偏移場的磁滯曲線外,於垂直於外加磁場的方向我們看到了一個特殊的雙重偏移(double shifted)的磁滯曲線,且偏移程度隨著反鐵磁層的厚度增加而增加。經由vector coil的量測我們進一步的發現其磁化量的翻轉行為乃是結合了可逆和不可逆的旋轉(rotation)機制。最後我們利用Stoner-Wohlfarth模型,實際地去模擬磁化量於翻轉過程中的能量變化,找出磁化量翻轉的臨界角度。
    In this experiment, the (001) IrMn/CoFe epitaxial bilayers were fabricated on Si substrates at room temperature by using Cu underlayers. A double shifted loop was observed at the axis perpendicular to the exchange bias direction. The dependence of anisotropy on the IrMn thickness was studied. The magnetization reversal was investigated by using vector coil measurements and calculations based on Stoner-Wohlfarth model. A combination of reversible and irreversible rotation was observed for the magnetization reversal along the hard axis. Critical angles and fields at which irreversible rotation occurred were obtained through simulations. When the hysteresis loops measured along other angles (θ) away from the exchange bias direction, the asymmetric magnetization reversal was observed by comparing with the simulated loops at the corresponding same angles. In addition, an unusual time dependent effect was observed in (001) IrMn/CoFe system for the drastically changes of the magnetic properties. Finally, for the further application in magnetic tunneling junction (MTJ), we have successfully deposited the MgO (001) structure by using the (001) IrMn/CoFe underlayers.
    Isbasedon: [1] S. S. P. Parkin, C. Kaiser, A. Panchula, P. M. Rice, B.
    Hughes, “Giant tunneling magnetoresistance at room
    temperature with MgO(100) tunnel barrier,” Nature Materials, vol. 3, pp. 862-867, Oct. 2004.

    [2] D. Y. Kim, C. G. Kim, C. O. Kim, M. Shibata, M. Tsunoda,
    and M. Takahashi, “Angular Dependence of Exchange Bias
    and Coercive Field in CoFe/MnIr Epitaxial Bilayers, ”
    IEEE Trans. Magn., vol. 41, pp. 2712-2714, Oct. 2005.

    [3] T. Mewes, B. Hillebrands, P. L. Stamps, “Induced fourfold
    anisotropy and bias in compensated NiFe/FeMn double
    layers,” Phys. Rev. B, vol. 68, pp. 184418-1~7, Nov. 2003.

    [4] C. H. Lai and Y. H. Wang, C. R. Chang, J. S. Yang, Y.D.
    Yao, “Exchange bias induced double shifted magnetization
    curves in Co biaxial films,” Phys. Rev. B, vol. 64, pp.
    094420-1~5, Aug. 2001.

    [5] P. Bolmqvist and K. M. Krishnan, H. Ohldag “Direct Image
    of Asymmetric Magnetization Reversal in Exchange-Biased
    Fe/MnPd Bilayers by X-Ray Photoemmission Electron
    Microscopy,” Phys. Rev. Lett., vol. 94, pp. 107203-1~4,
    Mar. 2005.

    [6] C.R. Chang, “Micromagnetic studies of coherent rotation with quartic crystalline anisotropy,” J. Appl. Phys. vol. 69, pp. 2431-2439, October, 1990.
    URI: http://nthur.lib.nthu.edu.tw/handle/987654321/31905
    Source: http://thesis.nthu.edu.tw/cgi-bin/gs/hugsweb.cgi?o=dnthucdr&i=sGH000935506.id
    Appears in Collections:[材料科學工程學系] 博碩士論文

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