报告题目：Magneto-optics, revisited

报 告 人：Rudolf Schaefer，Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Germany

时间地点：2025年7月11日10:00

报告地点：物理楼W260

内容摘要：Three aspects of magneto-optics are reviewed that have hardly be considered in the past:

(i) For Magneto-optical Kerr Effect (MOKE) magnetometry it will be shown that the obtained hysteresis loops need to be interpreted very carefully as they are measured locally, determined by the internal (not applied) magnetic field and by local magnetization processes [1]. MOKE hysteresis loops are therefore in most cases significantly different from integrally measured loops on the same specimen.

(ii) For wide-field MOKE microscopy numerous magneto-optical effects will be discussed that lead to intensity-based domain contrasts in the absence of analyser and compensator, which are the main optical components in conventional MOKE microscopy [2]. This includes the Transverse Kerr effect, a novel 45°-dichroic effect (Oppeneer effect), the Magnetic Linear Dichroism effect, and the Dichroic Gradient effect. All these effects require linearly polarized light for illumination. A further effect is the Magnetic Circular Dichroism effect that requires circularly polarised illumination.

(iii) On the example of ultrathin, exfoliated van der Waals material the role of the compensator as decisive optical element in MOKE magnetometry and microscopy will be discussed.

报告人简介：RUDOLF SCHAEFER received the diploma degree in materials science and the Ph.D. degree in engineering from the University of Erlangen, Germany, in 1985 and 1990, respectively. He then joined the IBM Research Center in Yorktown Heights, USA, and the Forschungszentrum Jülich, Germany, as a Postdoctoral Researcher in 1991 and 1992, respectively. In 1993 he moved to the IFW Dresden where he became head of the Department of Magnetic Microstructures in 2002. In 2011, he was appointed Adjunct Professor for Mag- netic Materials at the Institute for Materials Science, Technical University Dresden.His areas of interest span magnetic materials with a focus on magnetic microstructures and domain imaging by Kerr microscopy. He has published more than 240 technical articles in peer-reviewed journals, including book chapters, and he has coauthored the Springer textbook Magnetic Domains together with Alex Hubert.Prof. Schäfer serves as the chair of the Conference Executive Committee of IEEE Magnetics Society since 2017. In 2013 he was elected Distinguished Lecturer of the Magnetics Society. He furthermore is director of the evico magnetics GmbH.