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  • 學位論文

應用於超高密度磁性記錄媒體之鈷基合金與複合式記錄媒體相關研究

Co-based alloy and composite media for ultra-high density magnetic recording disk

指導教授 : 賴志煌

摘要


由於具備高容量、低成本的特性,硬碟裝置被普遍使用在電腦裝置以及各式消費性電子產品中,做為大量儲存數位資訊的重要媒介。硬碟片技術開發,最關鍵的一環,在於如何將碟片記錄密度持續提升,使硬碟機容量滿足大量化資訊儲存的需求,因此,開發兆位元等級之超高密度碟片技術,是過去十年碟片製造商及全球磁性研究領域上一個重大的課題,亦是本論文的主要研究方向。 本論文針對超高密度碟片相關技術進行開發與深入研究,研究課題著重於鈷基合金及複合式記錄膜層。第一部分探討磁性記錄層的材料選擇對於磁性記錄層的特性影響。比較不同氧化物添加於鈷鉻鉑合金,我們發現薄膜微結構中,具較低化學穩定性的氧化物,呈現較佳的晶界偏析程度,且磁晶粒間的磁交互耦合力明顯下降。透過X光吸收術分析,推測低化學穩定性的氧化物,在濺鍍過程中,容易釋出多餘的氧氣,使其成為氧化劑,促使晶界上的鉻氧化,令晶界上產生氧化鉻偏析,達到較好的磁交互力阻絕特性。 本論文第二部分著重在開發複合式記錄膜層結構。我們提出新穎式[鈷鉻鉑-二氧化矽/鉑]多層狀軟磁層結構,可透過改變鉑的厚度,控制軟磁層的垂直磁異向性及層間磁交互作用力。利用此複合結構,可以將碟片的磁性寫入場有效降低,並且提升其熱穩定性。我們同時藉由同步輻射光源的X光磁圓偏振二向性量測術,觀察複合薄膜的硬軟磁性層的翻轉非同調性。在碟片讀寫測試中,相較於傳統單一膜層結構,我們發現此複合式媒體在訊雜比及覆寫能力上,具有明顯提升。 論文最後一部分探討複合式膜層結構的磁性翻轉機制及關鍵量測技術之建立。我們透過X光磁圓偏振二向性量測術及磁性標定參雜層,得到具縱深解析之磁矩特性,隨著軟磁層厚度增加,直接在實驗端觀察並驗證由同調翻轉變成磁區壁輔助磁翻轉的行為改變。另一部份,我們使用了極化中子反射術,直接觀察軟磁層厚度對層間交互耦合力的影響,解析得到交互耦合力在縱深方向的強度分布。

並列摘要


Hard disk drives (HDDs) play a key role in mass data storage techniques, which are widely used in computer systems and various consumer electronics owing to their ad-vantages of low cost and high capacity. The growing demand for the HDD capacity drives the researches in increasing the areal density of the recording disk. This dissertation focuses on three main research topics to reach ultra-high density recording disks. The first topic investigates the Co-based alloy, which is currently used as the recording layer in commercial hard disks. By using first order reversal curves (FORCs), we found out distinct magnetization reversal behavior in the CoPtCr films with different oxide additives, including Ta2O5, SiO2 and their mixtures. Based on our results, increasing the Ta2O5-to-SiO2 ratio alters the inter-grain interaction from an exchange coupling (parallel) to a dipolar-field coupling (anti-parallel). During the sputtering process, the Ta2O5 additives release extra oxygen to induce the formation of CrOx. The reduced inter-grain exchange coupling strength by increasing Ta2O5 additives can be attributed to the increased volume concentration of oxides and/or the presence of the CrOx. The second topic aims at developing the advanced layer structure of composite media (or called exchange coupled composite (ECC) media) comprising magnetically hard and soft layers. We proposed a soft layer with a laminated structure (LSL, [Pt/CoPtCr-SiO2]5), which uniquely exhibits a tunable perpendicular anisotropy by modifying the Pt thickness. The incoherent reversal in the composite media with a LSL was directly observed by using X-ray magnetic circular dichroism (XMCD). With increasing Pt thickness, the anisotropy of LSL is reduced, which promotes the incoherent reversal of composite media to lower its switching field; however, further increasing the Pt thickness significantly reduced the in-terlayer coupling, and thus the assisting effect was suppressed. By optimizing the Pt thickness, the read-write test confirmed that the composite media with the proposed LSL presents superior recording performance over the conventional single layer media. The third topic focuses on characterizing the magnetization reversal and the interfacial coupling of composite media. The depth-dependent magnetization reversal in composite media was directly probed by means of XMCD technique with a magnetization marker. When the LSL thickness is increased, the transition of magnetization reversal from rigid magnet to exchange spring is observed. By using polarized neutron reflectometry (PNR), we reveal that the hard and soft layers are largely decoupled with the increase of the LSL thickness, and much more tightly coupled when the LSL thickness drops. This finding is in agreement with the fact that the change in reversal behavior of composite media can be attributed to the interfacial coupling strength.

參考文獻


73. Y. Choi, J. S. Jiang, J. E. Pearson, S. D. Bader, J. J. Kavich, J. W. Freeland, and J. P. Liu. Controlled interface profile in Sm-Co/Fe exchange-spring magnets. Applied Physics Letters, 91(7):072509, AUG 2007.
1. S. Iwasaki and Y. Nakamura. An analysis for the magnetization mode for high density magnetic recording. IEEE Transactions on Magnetics, 13(5):1272–1277, 1977.–1277, SEP 1977.
2. T. P. Nolan, Y. Hirayama, and M. Futamoto. “Improvement of Co71Cr19Pt10/Ti90Cr10 perpendicular recording media by independent optimization of film nucleation and growth processes.” Journal of Applied Physics, 79(8, Part 2a):5359–5361, APR 1996.
3. K. Sato, H. Wakamatsu, and M. Shinohara. Noise characteristics of CoCrTa/NiFe perpendicular recording media. IEEE Transactions on Magnetics, 29(6):3730–3732, NOV 1993.
4. N. Honda, J. Ariake, K. Ouchi, and S. Iwasaki. Low noise Co-Cr-Nb perpendicular recording media with high squareness. IEEE Transactions on Magnetics, 34(4):1651–1653, JUL 1998.

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