CAREER: Magnetic Anisotropy in Cobalt Alloy Films used in Hard Disk Recording Media

这份职业建议书涉及硬盘记录介质中使用的钴合金薄膜的磁性。该提案的研究部分的目标是确定在非平面衬底上沉积的薄膜中观察到的面内磁各向异性的起源，并且其在确定硬盘设备的记录性能中是关键的。与这一应用相关的教育目标旨在为学生在数据存储行业的职业生涯做好准备。数据以磁化图案的形式存储在硬盘中，写入溅射的钴合金薄膜中，通常沉积在铬底层上。为了改善磁头-磁盘界面的摩擦学行为，通常在溅射之前在硬盘衬底上引入表面划痕。然而，当将铬/钴合金双层膜溅射到有划痕或凹槽的衬底上时，发现平行于凹槽的面内矫直力、剩磁和方形度都较高。这种各向异性可能很大，即使对于浅凹槽也是如此，但各向异性的起源还不是很清楚。本研究的目的是阐明磁性薄膜的结构如何受衬底形貌的影响，并解释这是如何导致磁各向异性和影响器件性能的。此外，还将研究铬和钴合金之间的外延关系在确定磁性方面的重要性。这项研究对硬盘工业以及其他磁性薄膜器件，如磁阻读取头中的传感器或元件具有重要意义。这项工作将使用麻省理工学院纳米结构实验室建立的独特的亚微米光刻设备来制备具有可控亚微米形貌的大面积基板。这将允许测量在定义明确的衬底特征上沉积所产生的各向异性。拟议工作的主要目标是：-量化特定的衬底表面特征(槽、脊、台阶)对共合金薄膜中磁各向异性的贡献-将各向异性与薄膜的结构特征联系起来，包括颗粒形状、c轴取向、内应力以及铬层和钴合金层之间的外延关系-基于这些发现，提出控制薄膜中磁各向异性的方法-与工业合作伙伴合作，制造具有受控表面特征的磁介质，为了演示如何通过表面形貌的设计来改变硬盘的磁记录性能。这项建议的教育元素将侧重于发展学生与磁性行业之间的联系，目的是加强大学和行业之间的知识转移，并促进这一重要领域的学生的职业前景。这个价值数十亿美元的行业提供了许多就业机会，但电子材料科学和工程方面的传统教育和培训无法满足其对准备充分的毕业生的强烈需求。课程开发将包括在讲座和实验室课程中强调磁性设备和材料，引入一个包括来自行业的客座讲师和参观当地公司的短期课程，创建一个磁性设备兴趣小组来帮助学生和工业研究小组有效互动，以及面向高中教师的外联活动。

9875545RossThis CAREER proposal concerns the magnetic properties of thin cobalt-alloy films used in hard disk recording media. The goals of the research component of the proposal are to determine the origin of in-plane magnetic anisotropy, which is observed in films deposited over non-planar substrates, and which is critical in determining the recording performance of hard disk devices. The educational goals, related to this application, are designed to equip students for careers in the data storage industry.Data are stored in hard disks as magnetization patterns written into a sputtered cobalt-alloy thin film, usually deposited onto a chromium underlayer. Surface scratches are commonly introduced into hard disk substrates before sputtering to improve the tribological behavior of the head-disk interface. However, when the Cr/Co-alloy bilayer film is sputtered onto a scratched or grooved substrate, it is found that the in-plane coercivity, remanence and squareness are higher parallel to the grooves. This anisotropy can be large, even for shallow grooves, but the origin of the anisotropy is not well understood. The goal of this research is to clarify how the structure of the magnetic films is affected by substrate topography, and to explain how this leads to magnetic anisotropy and affects device performance. Additionally, the importance of the epitaxial relation between the Cr and the Co-alloy in determining magnetic properties will be investigated. This research has significance in the hard disk industry as well as in other magnetic thin-film devices such as sensors or elements in magnetoresistive readback heads.The proposed work will use unique submicron lithography facilities established at the NanoStructures Laboratory at MIT to prepare large-area substrates with controlled submicron topographies. This will allow the anisotropy created by deposition over well-defined substrate features to be measured. The major objectives of the proposed work are: - to quantify the contribution of specific substrate topographic features (grooves, ridges, steps) to magnetic anisotropy in Co-alloy films - to relate the anisotropy to structural features of the film, including grain shape, c-axis orientation, internal stress, and the epitaxial relation between the Cr and Co-alloy layers - based on these findings, to propose methods for controlling magnetic anisotropy in thin films - in collaboration with an industrial partner, to fabricate magnetic media with controlled surface features, in order to demonstrate how the magnetic recording properties of a hard disk can be modified by design of the surface topography.The educational element of this proposal will focus on development of links between students and the magnetics industry, with the aim of strengthening knowledge transfer between university and industry and enhancing the career prospects of students in this important sector. This multi-billion dollar industry provides many opportunities for employment, yet its strong demands for well-prepared graduates are not being met by traditional education and training in electronic materials science and engineering. Course development will include an emphasis on magnetic devices and materials in lectures and laboratory classes, the introduction of a short course including guest lecturers from industry and a visit to a local company, the creation of a Magnetic Devices interest group to help students and industrial research groups interact effectively, and outreach activities to high school teachers.***