【摘要】：在2004-2006年間，計算機硬盤中的數(shù)據(jù)記錄方式逐漸由水平磁記錄方式轉(zhuǎn)向垂直磁記錄方式�？墒请S著記錄密度的進一步提高，垂直磁記錄方式也在接近超順磁性的限制，因此，對下一代磁記錄方式的研究勢在必行。能量輔助磁記錄、比特圖形磁記錄和疊層瓦片式磁記錄是記錄密度有望超過1Tbit/in2的新型磁記錄方式。這三種磁記錄方式對介質(zhì)的磁性參數(shù)和微結(jié)構(gòu)的要求是各不相同的，相應的磁記錄過程也有較大的差異。因此，在綜合考慮介質(zhì)的熱穩(wěn)定性、信噪比和可寫入性的前提下，本文研究了比特圖形磁記錄和疊層瓦片式磁記錄所采用的介質(zhì)、記錄過程及密度極限，同時還分析了能量輔助磁記錄所使用的L10FePt介質(zhì)中的孿晶結(jié)構(gòu)對磁記錄性能的影響。 本文首先從實驗中觀察到的納米顆粒中的五重孿晶結(jié)構(gòu)出發(fā)，建立了一個解析的模型來理解孿晶結(jié)構(gòu)的存在對磁晶各向異性場的影響。計算結(jié)果表明，孿晶結(jié)構(gòu)的存在會大幅降低顆粒的磁晶各向異性場，，同時造成磁晶各向異性場的分布，這會降低介質(zhì)的熱穩(wěn)定性，增大反轉(zhuǎn)場的分布寬度，降低信噪比。這個問題的研究對理解磁晶各向異性場的分布有普遍的意義。 使用雙顆粒模型對交換耦合（ECC）介質(zhì)的反轉(zhuǎn)特性進行了研究，分析了介質(zhì)磁性參數(shù)與反轉(zhuǎn)場的關系，為設計熱穩(wěn)定性和可寫入性都良好的ECC介質(zhì)提供了指導。隨后，分別對垂直薄膜介質(zhì)和ECC介質(zhì)進行了疊層瓦片式磁記錄過程的模擬，統(tǒng)計了不同記錄密度下的信噪比，發(fā)現(xiàn)ECC介質(zhì)具有更高的信噪比和密度極限，同時還對ECC介質(zhì)的磁性參數(shù)作了進一步的優(yōu)化。 在對光刻法制備的比特圖形介質(zhì)（BPM）的磁記錄過程的模擬中，研究了實現(xiàn)寫入同步的時間窗口和對磁道偏移量的容忍度，發(fā)現(xiàn)降低由介質(zhì)非均勻性造成的磁晶各向異性場的漲落有利于比特的正確寫入。在對離子輻照法制備的BPM介質(zhì)的磁記錄模擬過程中發(fā)現(xiàn)，大幅降低比特之間被輻照區(qū)域的磁性質(zhì)、對各個比特進行磁性隔離是實現(xiàn)正確寫入的關鍵。通過優(yōu)化系統(tǒng)參數(shù)和磁性參數(shù)，對不同密度的BPM介質(zhì)的磁記錄結(jié)果進行分析，可以預測離子輻照法制備的BPM介質(zhì)的記錄密度極限大約是3.0Tbit/in~2。
[Abstract]:From 2004 to 2006, the data recording in computer hard disk gradually changed from horizontal magnetic recording to vertical magnetic recording. However, with the further improvement of recording density, the perpendicular magnetic recording is approaching the limit of superparamagnetism. Therefore, it is imperative to study the next generation magnetic recording. Energy assisted magnetic recording, bit pattern magnetic recording and laminated tile magnetic recording are new magnetic recording methods, which are expected to exceed 1Tbit/in2. The three kinds of magnetic recording methods have different requirements on the magnetic parameters and microstructure of the medium, and the corresponding magnetic recording processes are different. Therefore, on the premise of considering the thermal stability, signal-to-noise ratio and writeability of the medium, the recording process and the density limit used in the bit pattern magnetic recording and laminated tile magnetic recording are studied in this paper. The effect of twin structure in L10FePt medium used in energy-assisted magnetic recording on the magnetic recording performance is also analyzed. Based on the quintuple twin structure observed in the experiment, an analytical model is established to understand the influence of the twin structure on the magnetocrystalline anisotropy field. The results show that the existence of twin structure can greatly reduce the magnetocrystalline anisotropy field of particles and cause the distribution of magnetocrystalline anisotropy field, which will reduce the thermal stability of the medium, increase the distribution width of the inversion field and reduce the signal-to-noise ratio (SNR). The study of this problem is of general significance for understanding the distribution of magnetocrystalline anisotropic fields. The inversion characteristics of the exchange-coupled (ECC) medium are studied by using a two-particle model. The relationship between the magnetic parameters of the medium and the inversion field is analyzed, which provides guidance for the design of the ECC medium with good thermal stability and writeability. Then, the vertical thin film medium and ECC medium are simulated by laminated tile magnetic recording process, and the SNR of ECC medium under different recording densities is calculated. It is found that ECC medium has higher SNR and density limit. At the same time, the magnetic parameters of ECC medium are further optimized. In the simulation of the magnetic recording process of bit graphics medium (BPM) prepared by photolithography, the time window of writing synchronization and tolerance to track offset are studied. It is found that decreasing the fluctuation of magnetocrystalline anisotropic field caused by medium inhomogeneity is beneficial to the correct writing of bits. In the process of magnetic recording simulation of BPM prepared by ion irradiation, it is found that the key to correct writing is to greatly reduce the magnetic properties of irradiated regions between bits and to isolate the magnetic properties of each bit. By optimizing the system parameters and magnetic parameters, the magnetic recording results of BPM medium with different densities are analyzed. It can be predicted that the limit of recording density of BPM medium prepared by ion irradiation is about 3.0 Tbit / n ~ (2).
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TP333

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