隨著個人電腦(PC)的普及與發展，硬碟裝置兼具低成本與高記錄容量，長期以來是常見和廣泛使用的大容量數據儲存設備之一。然而進入後PC時代，在以小尺寸為主要訴求的攜帶式裝置上硬碟逐漸失去了競爭優勢；幸而其在雲端儲存(在線儲存服務)的產業中另闢一片天地，並持續蓬勃發展。數十年來，硬碟記錄密度不斷提高，其中磁性奈米顆粒的尺寸持續縮小並逐漸逼近理論極限；當尺寸小到一定程度終將面臨超順磁現象的臨界尺寸而失去磁組態的熱穩定性。下一世代的磁記錄媒體，序化鐵鉑合金作為關鍵材料，相對於商用鈷系合金具有較高的磁晶異向性能夠在更小的尺寸下維持熱穩定性。本論文主要研究序化鐵鉑合金的序化相轉變與其微觀結構的操控以滿足相關產業的要求。
第一部分研究為針對x光繞射儀(XRD)圖譜的進階處理，提出穩固且合理的鐵鉑合金序化度估算方法。對於目前最常被提及的估算公式：S ≈ 0.85 (A001/A200)1/2，提出兩點修正。其一：在繞射峰積分強度的表示式中加入Nuni(單位晶包數量)項。其二： 對繞射峰積分時，不可直接對θ-2θ圖譜積分。如此一來，繞射峰積分面積比值A(100)/A(200)是序化度與序化體積比兩種因子交錯貢獻的結果。序化體積比可經由繞射峰積分面積比A(111)/A(222)獲得。然而目前本方法受限於XRD繞射峰值訊雜比不佳與量測極端耗時的限制而無法實際應用，期望未來能有更好的解決方法。
第二部分研究目的在加速鐵鉑合金的序化相轉變。我們開發一介穩態的銀鉑合金薄膜，並從相關元素之擴散係數差異的前提下，提出[鐵/銀鉑]雙層膜，在相對低之後退火溫度下銀鉑層即會分解產生孔隙，藉此孔隙達到加速鐵鉑合金序化相轉變的過程。介穩態的銀鉑合金薄膜在相對低的退火溫度下分解產生的孔隙，趨使鐵原子擴散進入加速鐵鉑之混合，促進序化鐵鉑相的生成。利用即時升溫的X光繞射儀觀察記錄[鐵/銀鉑]雙層膜轉變為序化鐵鉑合金與元素銀的過程，更透過第一原理的計算作為其可行性的佐證。我們在僅僅230度退火處理，透過穿透式電子顯微鏡與略角X光繞射儀分別直接地觀察到鐵鉑(銀)混合物的形成與序化鐵鉑相的成核。藉由此一銀鉑合金的引入，在350度退火處理下獲得以(001)優選取向為主的序化鐵鉑合金薄膜，其垂直矯頑場約為13.3 kOe。
研究的第三部分著重於碳摻雜序化鐵鉑合金薄膜的微觀結構操控。透過不同碳摻雜含量的序化鐵鉑合金之微觀結構變化，我們推論碳摻雜量的增加有助於形成良好的晶粒狀分隔，然而並未有效降低晶粒尺寸。並在隨後的研究發現晶粒尺寸的降低可以透過較慢的薄膜成長速率達成。隨後以不同的薄膜成長速率，鍍製厚度僅1奈米的鐵鉑合金以模擬薄膜成長時的成核階段。從微觀結構的改變可以發現，較慢的薄膜成長速率導致較高的成核密度，最終形成較小的晶粒尺寸。依此結果我們提出一套成長機制，其包含成核與結晶成長理論以及摻雜物析出行為的假說。另一方面，下層的表面粗糙化亦可有效的提高成核密度，我們依此開發具有相同晶體結構、更匹配晶格常數與較小尺寸的碳摻雜晶粒狀錳鉑合金作為種晶層，此碳摻雜錳鉑合金確實有效地降低鐵鉑合金的尺寸。此方法深具潛力，使我們更可以在較少的碳摻雜或更高的升溫濺鍍環境下形成晶粒狀的鐵鉑合金。然而根據我們所提出的成長機制，碳摻雜的序化鐵鉑合金必然會形成球狀晶粒；對此我們開發電漿處理的表面清潔技術將樣品表面的析出碳移除。應用此技術於FePt/FePt:C雙層膜中的FePt:C下層，並在此雙層膜中觀察到部分柱狀晶的生成，顯示此一電漿表面處理具有開發碳摻雜之柱狀鐵鉑晶粒的潛力。

Hard disk drive (HDD) is one of the most common and widely used mass data storage devices for a long period due to low cost and high recording capacity. The flourishing application is contributable to and coexists with the era of personal computer (PC). Nowadays, HDD though is not the top choice for portable electronic devices in post-PC era because of the size dimension; wile the rise of CLOUD storage (online storage service) raises additional demands on HDDs. For decades, the increase in recording density of HDD never stops, but a limitation is foreseen along with the demands on recording capacity, which requires recording granules approaching so-called superparamagnetic limit. For next generation magnetic recording technology, L10 FePt seems promising to against the thermal fluctuation at smaller size in comparison with current Co-based commercial products for its higher magnetocrystalline anisotropy. This dissertation is about the ordering of L10 FePt and the related microstructure control to meet industrial requirements.
We first established a solid and rational evaluation of ordering degree (S) for FePt from x-ray diffractometry (XRD) pattern. The most referred formula: S ≈ 0.85 (A001/A200)1/2 was modified by two considering: 1. Incorporating Nuni (number of unit cell) into integrated intensity equation. 2. The intensity can’t be directly integrated from θ-2θ patterns unless the oriental distribution is characterized. Correspondingly, the integrated intensity ratio of A(100)/A(200) becomes a function of both S and disorder-to-order volumetric ratio. The latter can be obtained alternatively by A(111)/A(222). This approach is however inapplicable based on our proposed scan geometry for poor signal-to-noise ratio and enormous time-consumption. A better solution for the data acquisition is demanded.
Second, we studied the enhancement of disorder-to-order phase transition of FePt. We deposited the metastable AgPt layer adjacent to the Fe layer and addressed the importance of vacancies to the disorder-order transition of FePt at reduced temperatures on the basis of a kinetic diffusion model. The decomposition of the metastable AgPt phase creates excess vacancies during the post-deposition annealing process. This accelerates the intermixing between Fe and Pt hence the nucleation of L10 FePt. The evolution of phase transformation from AgPt-Fe to L10 FePt-Ag was monitored by in situ high temperature X-ray diffractometry (XRD) and was also validated by first-principles calculations. The intermixing between Fe and Pt and the nucleation of L10 FePt after annealing at 230˚C were directly observed by transmission electron microscopy and grazing incidence XRD, respectively. With the assistance of the decomposition of AgPt, we obtained a (001)-dominated L10 FePt film with an out-of-plane coercivity as large as 13.3 kOe after annealing at a temperature as low as 350˚C.
The third is a focus on the microstructure control of L10 FePt with C as the segregants. FePt:C films with varying C concentration indicates that more C leads to better planner isolation but no size reduction. The latter is then achieved by lowering deposition rate. FePt (1 nm) at varying deposition rates was fabricated to mimic the nucleation stage. The results suggested that the higher density of nuclei at lower deposition rate leads to smaller granular size of FePt:C. We therefore constructed one growth mechanism of FePt:C based on nucleation and growth model and the hypothesis of impurity exclusion during film growth. Another effective way leading to higher nucleation density is to grow on a rougher surface. Therefore, a L10 MnPt:C seed-layer having the same structure and accommodate lattice but smaller size with L10 FePt was developed. It is successfully reduce the granular size of FePt:C. Moreover it shows potential in achieving granular FePt:C films at reduced C concentration or higher substrate temperature. Our growth model implies a spherical nature of FePt:C, we therefore developed a surface clean process by controlling a weak plasma to remove only the top surface C accumulation. Applying this treatment on the bottom layer in FePt/FePt:C bi-layers shows good potential for columnar growth.

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