Micromagnetism and Microstructure of Ferromagnetic Thin Film Systems

这个项目的目标是利用自旋极化低能电子显微镜和磁光克尔效应测量相结合的新技术，从微观上理解(1)超薄膜系统的微结构与其磁性之间的相互关系，以及(2)这些性质与薄膜厚度、表面活性剂、温度和磁场强度等参数的关系。主要研究了以下几个问题：(1)界面的颗粒结构和粗糙度以及表面的清洁或吸附对磁畴结构的影响；(2)铁磁层之间通过非磁性或反铁磁隔离层的层间耦合；(3)微观结构对磁畴壁运动的影响；(4)亚微米尺度的磁系几何形状对磁畴结构和壁面运动的影响。这些结果不仅对于基本理解降维的铁磁性，而且对于磁记录和传感器件的开发和优化都是重要的。在过去，所有的电子设备都是基于电子带电荷这一事实。近年来，人们努力开发利用电子也有自旋这一事实的器件。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。下个世纪需要更高的存储密度和更小的传感器。为了实现这一目标，必须更好地了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。使用自旋极化低能电子显微镜的新方法可以很好地实现这一点，该方法可以同时成像自旋分布和微观结构。这项研究不仅将对新的高科技“自旋电子学”的发展做出重大贡献，同时还将为这一具有重要经济意义的领域培养学生。

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.***