Micromagnetism and Microstructure of Ferromagnetic Thin Film Systems

本项目的目标是利用自旋极化低能电子显微镜结合磁光克尔效应测量的新技术，从微观上理解(1)超薄膜系统的微观结构与其磁性之间的相互关系，以及(2)这些特性对薄膜厚度、表面活性剂、温度和磁场强度等参数的依赖关系。本研究主要关注以下问题：(i)晶粒结构和界面粗糙度以及清洁或被吸附物覆盖的表面对磁畴结构的影响；（ii）铁磁层之间通过非磁性或反铁磁间隔的层间耦合；（iii）微观结构对畴壁运动的影响；（iv）畴结构和壁运动对亚微米尺度磁性系统几何形状的依赖。研究结果不仅对认识降维铁磁性具有重要意义，而且对磁记录和传感器件的开发和优化具有重要意义。过去，所有的电子设备都是基于电子带电荷这一事实。近年来，人们花了很大的努力来开发利用电子也有自旋这一事实的装置。这已经导致了基于超薄金属薄膜的新型高密度信息存储介质和传感器的出现。下个世纪还需要更高的存储密度和更小的传感器。为了达到这一目标，必须更好地理解自旋系统的性质对其微观结构的依赖，因为它们是紧密耦合的。利用自旋极化低能电子显微镜可以同时成像自旋分布和微观结构。这项研究不仅将对“自旋电子学”这一高新技术的发展作出重大贡献，同时还将为这一重要的经济领域培养学生

9818296BauerThe goal of this project is the microscopic understanding of (1) the interrelation between the microstructure of ultrathin film systems and their magnetic properties and (2) of the dependence of these properties upon parameters such as film thickness, surfactant, temperature and magnetic field strength, using the novel technique of spin-polarized low energy electron microscopy combined with magneto-optic Kerr effect measurements. The study focuses on the following problems: (i) the influence of grain structure and roughness of the interface and of the clean or adsorbate-covered surface on the magnetic domain structure, (ii) the interlayer coupling between ferromagnetic layers through nonmagnetic or antiferromagnetic spacers, (iii) the influence of the microstructure on the domain wall motion and (iv) the dependence of the domain structure and of the wall motion on the geometry of the magnetic system in submicron dimensions. The results are important not only for the basic understanding of ferromagnetism in reduced dimensions but also for the development and optimization of magnetic recording and sensing devices. %%%In the past all electronic devices were based on the fact that the electron has a charge. In recent years great efforts were made to develop devices which make use of the fact that the electron also has a spin. This has lead already to new high density information storage media and sensors based on ultrathin metallic films. Still higher storage densities and smaller sensors are needed in the next century. To reach this goal the dependence of the properties of spin systems upon their microstructure must be better understood because they are intimately coupled. This can be best achieved using the novel method of spin-polarized low energy electron microscopy which images simultaneously spin distribution and microstructure. The study will not only contribute significantly to the development of the new high technology "spintronics" but at the same time trains students for this economically important field.***