Fudan University, Shanghai, China
The Hall Effects Edwin Hall Never Imagined
The anomalous Hall effect (AHE) is one of the oldest and most prominent transport phenomena in magnetic materials. Yet, AHE has remained unresolved for more than a century because its rich phenomenology defies standard classification, prompting conflicting claims of the dominant mechanisms. On the other hand, the more recently discovered spin Hall effect (SHE) has expeditiously attracted a great deal of attention because of its potential applications in spin current devices. Various methods have been developed to generate and detect the SHE, and search for materials with larges spin Hall angles. These efforts notwithstanding, reliable and accurate determination of spin Hall angle remains challenging. In this lecture, I will first give a comprehensive discussion on the basic concepts on AHE and SHE. Exploiting the attributes of epitaxial magnetic thin films, I will then explain how to control independently the different scattering processes through temperature and layer thickness and to identify unambiguously the intrinsic mechanism as well as the extrinsic mechanisms of the AHE. Finally, based on the understanding of the microscopic mechanisms of the AHE, I will describe how we develop a new method using the H-patterns to measure quantities inherent to the SHE.