| 题名 | 高密度磁光存储中膜层的光、热、磁性能优化研究 |
| 作者 | 王现英 |
| 学位类别 | 博士 |
| 答辩日期 | 2005 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 干福熹 |
| 关键词 | 磁光存储 光、热、磁优化设计 交换耦合双层膜 中心孔探测型磁超分辨 FeR薄膜 |
| 其他题名 | Research on the optical, thermal and magnetic optimization of the multilayer in high density magneto-optical storage |
| 中文摘要 | 磁光存储作为一种与全光存储、磁存储并存的存储方式，具有存储密度潜力大、可移动、可擦重写、寿命长等诸多优点，在计算机外存以及消费光电子领域都有广泛的应用。磁光存储信息写入过程是热磁写入，即以聚焦激光加热存储介质，使之达到补偿温度或居里温度，同时加一外磁场来使记录磁畴翻转；而读出过程是利用磁光克尔效应来读出的。可见，磁光存储过程涉及众多的光学、热学、磁学现象。对磁光存储的研究要围绕存储体系光学、热学、磁学性能的优化而展开，通过这些性能的优化使体系达到最高的存储密度。短波长磁光存储、磁超分辨磁光存储、磁畴放大读出技术、畴壁移动检测读出技术、磁超分辨近场结构存储技术、光磁混合存储技术是近年来磁光存储的研究热点，是未来高密度磁光存储的发展方向。本文在第一章具体介绍了这些技术的原理及优缺点。我们的研究正是以磁光存储系统性能优化为依据而开展的。本文主要内容包括以下几个方面的工作：首先是磁光盘光学、热学优化设计的方法及优化程序的撰写；其次是用于中心孔探测型磁超分辨的交换祸合膜磁学性能的优化设计及程序撰写；再次是交换祸合双层薄膜超分辨效应的实验研究；最后对用于光磁混合存储的FeRt薄膜作了制备工艺和性能的研究。以RE-TM作为蓝光磁光存储的介质时，由于其短波长时克尔角下降，会井撰绷．皿翻缚噪比下降，因此需要对膜层结构进行光学、热学结构的优化设计。我们用光学导纳特征矩阵法对新型蓝光盘进行了光学优化设计，通过膜层匹配得到了较大的品质因子；基于麦克斯韦方程和热传递方程，用有限元和差分法，计算了聚焦激光作用下磁光层的温度分布。结果表明，在紧贴记录层处加一层10nm左右的Al作为热控制层，可以使相同读出激光功率下记录层的温度大大降低，因此可以提高读出激光的阈值功率，从而提高读出载噪比。本文第二部分的研究主要是通过理论计算确定在中心孔探测型磁超分辨中各单层膜的性能对交换祸合双层薄膜的性能的影响，通过对单层膜磁性的优化使双层薄膜能够实现超分辨读出效应。用分子场理论计算和拟合了不同温度下GdFeC。、TbFeCO薄膜的磁参数；根据双层交换藕合膜的连续模型计算了读出层和记录层的磁参数对双层膜内磁化方向分布的影响；最后，分析了不同温度时双层膜内磁化方向的分布，从理论上说明：在单层膜的磁性能具备一定条件后，读出层的磁化方向随温度升高会发生由平面到垂直的转变。根据理论计算的结果我们知道，要使双层藕合薄膜实现超分辨读出效应，读出层补偿温度最好在100－00℃之间，而记录层的补偿温度应该低于室温。在实验过程中，我们反复调整制备工艺条件后，得到补偿温度为480K的GdFeCo薄膜和补偿温度小于室温的TbFeCo薄膜，然后在相同的工艺条件下制备了GdFeCo／TbFeCo交换藕合双层膜，并测量了加温时双层膜的克尔回线。结果表明，当温度为413K时GdFeC。薄膜磁化方向由平面转变为垂直磁化。实验结果很好的验证了前面的理论计算结果。为了尽可能提高存储密度，要求存储介质的超顺磁极限尺寸尽量减小，各向异性能尽可能大。Ll。有序FePt薄膜具有非常大的矫顽力和各向异性常数，因此，具有很高的记录密度潜力，是下一代磁存储介质的理想选择。在本文中，我们研究了Llo有序垂直各向异性FePt薄膜的制备工艺，在MgO衬底上成功地I！制备了垂直各向异性的FePt薄膜，其矫顽力大于7000Oe。研究结果还表明，FePt薄膜的磁性受其结构有序化程度的影响，有序化程度越高，则薄膜矫顽力越大。 |
| 英文摘要 | As one of the most popular storage media, magneto-optical (MO) storage has many advantages. For example, it has large capacity potentials and long life-span; also, it is movable and rewritable. Consequently, MO disks are widely used in computers and other consumptive photoelectron fields. The writing process of MO storage is thermal-magnetic writing, a laser beam is used to heat the storage medium to its compensation or Curie temperature and at the same time an external field is applied to write information in the medium. Magneto Kerr effect is used for the reading process. It is not hard to see that many optical; thermal and magnetic principles are involved in the writing and reading process of MO storage. Many research activities concerning MO storage have been done recently to get larger recording density and capacity. To get the largest density, the optical, thermal, and magnetic properties of the MO system must be well optimized. Short wavelength recording; magnetically induced super resolution (MSR) technolology: Magnetic domain expansion detection MO storage (MAMMOS); Domain wall displacement detection MO storage (DWDD); Super-resolution near-field structure MO storage (Super-RENS) and Heat assisted magnetic recording (HAMR) are among the hottest research topics in the last few years. These technologies stand for the future directions of the MO storage. In the first chapter of this thesis, the principles and advantages of these technologies were introduced in detail. The research in this thesis was also surrounding the optimization of the MO system. Firstly, we studied the optimization method of the optical and thermal properties of MO disk; secondly, the optimization of the magnetic properties of the exchange-coupled double layer (ECDL) films for center aperture type MSR was carried out; thirdly, the super resolution effect of the ECDL films was studied through experiments; at last, the preparation process and the properties of the Llo ordered FePt films were studied. The conventional rear-earth transition-metal (RE-TM) MO medium has a relatively smaller Kerr rotation angle in the blue region than in the red. If it is still used as the medium of the short wavelength recording, the conventional MO disk structure must be optimized to get a larger carrier to noise ratio (CNR). The optical admittance characteristic matrix method was used to optimize the optical properties of the MO disk. Through the adjust of the film thickness, large figure of merit of the multilayer system was obtained. Based on the Maxwell equation and the heat transfer equations, we calculated the temperature profile of the MO layer. The calculation result showed that new disk structure with a thermal control layer was very useful in preventing the excessive temperature increase of the MO film under blue laser. Thus the maximum value of the read out laser would increase and large CNR could be obtained. In the second part of our research work, the object was to optimize the magnetic properties of the GdFeCo/TbFeCo ECDL film to realize magnetically induced super resolution effect. According to the mean-field theory and some experimental results, the magnetic parameters of GdFeCo ,TbFeCo film under different temperatures were fitted. Then using the continuum model of the ECDL film, we calculated the effect of the magnetic properties of the monolayer film on the magnetization profile of the double layer film. At last, the directions of the magnetization of the ECDL films under different temperatures were calculated. The calculation result showed that when the monolayer film was under certain conditions, the direction of the magnetization of the readout layer changed from in-plane to out of plane when the temperature rose. According to the result of our calculation, to get the magnetically induced super resolution effect in ECDL films, the compensation temperature of the readout layer should be about 100-200 °C while that of the recording film should be below the room temperature (RT). During the experimental process we adjusted the film preparation process for many times and got GdFeCo and TbFeCo film with right compensation temperature (480 K and below RT). Then the GdFeCo/TbFeCo double layer films were prepared under the same process and the Kerr effect was measured. The result showed that when the temperature was 413 K, the GdFeCo film was perpendicularly magnetized, which demonstrated the reorientation of the GdFeCo film. The experimental results showed agreed well with the calculated results. To fully develop the recording density, the extreme size of the super paramagnetism limit should be reduced and the anisotropy energy of the storage medium should be enlarged. Llo ordered FePt film has large coercivity and anisotropy constant, thus it can be recorded under extremely high density. We studied the preparation process of the Llo ordered FePt film with perpendicular anisotropy and prepared perpendicular FePt film successfully, the coercivity of which was above 7000 Oe. The result also showed that the magnetic properties of FePt film depended on the film structure. The more ordered of the film structure, the larger the coercivity. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15355]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王现英. 高密度磁光存储中膜层的光、热、磁性能优化研究[D]. 中国科学院上海光学精密机械研究所. 2005. |
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