高密度垂直磁记录薄膜中微结构不均匀性及对其磁性质的影响

Recently, L10-FePt films have been intensively studied as candidates for perpendicular magnetic recording with ultrahigh-density magnetic data storage. Many useful results have been obtained on lowering the ordering temperature, improving the (001) texture and controling the size of the grains for FePt films. However, there is no verdict about the effects of crystal strain, microstructures of interface and grains on the magnetic properties of L10-FePt films.. In the present project, FePt films and graded media with different microstructures will be obtained on different substrates at different depositing conditions. Depth dependence of crystal strain will be investigated by gracing incidence X-ray diffraction and TEM. Accumulation of atoms, roughness and defects at the interface and surface will be studied by X-ray reflectivity, diffuse scattering and TEM. Morphology, strain and compostional inhomogeneity of the crystal grains will be analyzed by the combination of the extended x-ray-absorption fine structure with EDX,TEM and AFM. The aim of the project is to investigate the affecting mechanism of microstructures on the magnetic properties in L10-FePt films. Results will provide a scientific basis for the growth of the satisfactory FePt-based media meeting the requirement of application。

近年来，L10-FePt系合金膜因其在高密度垂直磁记录方面的应用前景而得到物理、材料、器件等各方面研究者的关注，获得了很多有意义的结果。但尚有一些关键机理性问题存在争议，如晶格应变、界面效应等微结构不均匀性对磁性质的影响方面的研究还比较缺乏，这成为该材料实用化的瓶颈。本项目拟通过改变衬底材料、覆盖层、生长温度等生长参数，获得具有不同微结构的FePt薄膜，利用同步辐射掠入射X射线衍射结合TEM分析薄膜的晶格应变及深度分布，利用X射线小角反射和漫散射结合TEM获得界面处原子堆积、粗糙度等信息，利用同步辐射X射线近边精细结构、能量色散X荧光光谱结合TEM和AFM分析FePt薄膜晶粒的形貌、应变、成分分离等。细致研究晶格应变、界面效应及成分分布等微结构不均匀对L10-FePt薄膜的磁各向异性、饱和磁矩、矫顽场等磁性质的影响机理，为该材料在高密度垂直磁记录方面的应用提供依据。

本项目研究了不同沉底上制备FePt有序薄膜的微结构和磁性质；研究了不同方法制备FePt有序薄膜的微结构和磁性质；着力研究了温度效应、晶格应变分、和晶粒尺寸分布对FePt薄膜磁性质的影响。该项目研究获得了不同制备方法对FePt磁性能的影响机理，明确了制备方法的优化方向，获得了晶格应变及晶粒效应对磁性质的影响机理。研究发现，在MgO（001）单晶基片上，共溅射和多层膜方法都获得了（001）取向的L10-FePt有序薄膜，有序度均接近1.0。两种方法获得的薄膜垂直各向异性常数Ku 分别为4.25×10^7 和7.9×10^7 erg/cc，垂直矫顽场分别为1157Oe和22500Oe，矩磁比分别为0.855和0.993。多层膜方法获得的L10-FePt薄膜具有大的垂直各向异性和矫顽场被归因于多层膜方法制备的薄膜较多的截面驱动力导致薄膜更加弛豫，晶格更加完整且颗粒度较好。在此基础上，在SrTiO3（001）衬底上利用多层膜方法制备了L10-FePt薄膜，获得了达到理论预期的超高垂直磁各向异性（6.1×10^8ergs/cc），且晶格颗粒度更加均匀，相关的研究为L10-FePt材料在垂直磁记录方面的应用提供了依据，为下一步FePt合金和钙钛矿锰氧化物异质结构研究打下了基础。