Fudan University, China
The anomalous Hall effect (AHE) is one of the oldest and most prominent transport phenomena in magnetic materials. However, the microscopic mechanism of the AHE has remained unresolved for more than a century because its rich phenomenology defies standard classification, prompting conflicting claims of the dominant processess. We differentiate these processes through temperature-dependent measurements on epitaxial Fe, Ni, Co, and NixCu1-x films of varying thickness , . The results allow an unambiguous identification of both intrinsic and extrinsic mechanisms of the anomalous Hall effect. The more recently discovered spin Hall effect (SHE) has 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 large spin Hall angles. These efforts notwithstanding, reliable and accurate determination of spin Hall angle remains a challenge. In this lecture I will first give a comprehensive discussion on the basic concepts of AHE and SHE. Expoliting the attributes of epitaxial magnetic thin films, I will then explain how to control independenly the different scattering processes through temperature and layer thickness and to identifiy unambiguously the intrinsic and extrinsic mechanisms of the AHE. Finally, based on the understanding of the microscopic mechanisms of the AHE, I will describe how we developed a new method using H-patterned films to measure quantities inherent in the SHE.  Y. Tian, L. Ye, and X, Jin, “Proper scaling of the anomalous Hall effect,” Phys. Rev. Lett. 103, 087206 (2009), doi : 10.1103/PhysRevLett.103.087206.  D.-Z. Hou, G. Su, Y. Tian, X. Jin, S. A. Yang, and Q. Niu, Phys. Rev. Lett. 114, 217203 (2015), doi: 10.1103/PhysRevLett.114.217203.
Xiaofeng Jin received the B.S. and Ph.D. degrees in physics from Fudan University in 1983 and 1989, respectively. Concurrently, he was at Laboratoire pour l’Utilisation du Rayonnement Electromagnetique (LURE) in Orsay, France, from June 1987 to May 1988. He joined the faculty at the Department of Physics, Fudan University, in 1989, and became full professor in 1995. He has been a visiting scholar at many research institutes including University of California, Berkeley; Chalmers University of Technology, Goteborg; Max-Planck Institute for Microstructure, Halle; University of Utah; Institute for Materials Research, Tohoku University, Sendai; and Hong Kong University of Science and Technology. He has published over 100 technical articles in peer-reviewed journals, including book chapters and review articles, and has given more than 50 invited presentations at international conferences. He served as the chair of the 21st International Colloquium on Magnetic Films and Surfaces (ICMFS) in 2012 and on the advisary committes and program committees of various international conferences on magnetism and spintronics. He is currently the chair of the International Union of Pure and Applied Physics (IUPAP) Magnetism Commission C9. He is a member of the IEEE Magnetics Society.
Imagine a future in which food is used to activate specific immune reactions in a human body based on an external noninvasive magnetic stimulus. Dream of a material that stores and releases energy reversibly by temperature changes between day and night. These visions may be realized by using magnetic nanoparticles that are functionalized to be biocompatible, environmentally stable and recyclable, self-healing, and low-cost.
In this presentation I will discuss the basic concepts of magnetic nanomaterials and their magnetic properties with a focus on how to tune specific parameters in a controlled fashion to achieve the dreams of the future. I will highlight state-of-the-art experimental technologies that allow us to understand microscopic properties and interactions in relation to electronic structure changes caused by changes in size, shape, and composition of nanomaterials. Then I will discuss how this understanding is used when nanomagnets are functionalized for targeted drug delivery or composed to form macroscopic materials for new energetic applications like magnetic refrigeration. I will demonstrate that the seemingly complex behavior of hybrid metal/metal, metal/oxide, or oxide/oxide interface materials can be understood from the three fundamental interactions in magnetism: magnetic exchange interaction due to orbital overlap, spin-orbit interaction due to inner- and intra-atomic relativistic corrections (e.g., crystal field effects) and the long-range magnetic dipolar interaction. Several examples will be presented, including the formation of above-room-temperature ferromagnetic interface layers between low-temperature antiferromagnetic layers and the evolution of lattices of magnetic textures (skyrmions) in confined dimensions. The talk will end with an episode in the life of an imaginary golf-playing couple in the year 2040 who use their “Smart Magnet” (SMAG) phone to energize and heal their bodies on the green.