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学术活动

学术报告:Studying the long-range magnetic interactions between nanoparticles in hierarchical structures
2019-03-15

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  时间:2019年3月15日(周五),上午10:00-11:00

  地点: 教三楼321室

  主讲人:Peter J. Klar

  主办单位: 物理系

  活动/主讲人简介:

  

  Peter J. Klar 教授1993年毕业于德国汉堡大学(University of Hamburg)物理系,获Diplom学位。1996年获英国东英吉利大学(University of East Anglia)物理学院博士学位。1997-1998年先后在英国东英吉利大学和萨里大学(University of Surrey)做博士后研究工作。1998-2006年在德国马尔堡大学(University of Marburg)做科研工作, 并任课题组长。2004年12月, 取得高等学校教授资格(Hablitation), 2005年2月始任讲师。2006年至今,任职德国吉森大学(University of Giessen)实验物理研究所教授, 并任微纳制备实验室主任。

  Peter J. Klar教授研究领域包括半导体光谱学、垂直腔发射半导体激光器、新型半导体材料与器件、微纳尺度半导体材料和磁性掺杂半导体材料中的光电子学和自旋电子学、半导体微纳结构的制备等。建立了德国Giessen大学实验物理研究所的微纳制备实验室。Peter J. Klar教授在Phys. Rev. Lett., J. Am. Chem. Soc., Appl. Phys. Lett.等国际知名期刊上发表学术论文140余篇,并主编3部专著的主要章节。Peter J. Klar的H因子达到21,是国际上具有相当影响力的科学家。

  Peter J. Klar教授一直主持承担德国物理学会(DPG)、德国研究委员会(DFG)的多项重要研究项目,并为物理学、半导体材料学领域多种国际期刊特邀审稿人。

  报告摘要:

  By combining top-down lithographic techniques with the meniscus-force deposition method, hierarchical structures consisting of defined regular elements on length scales from a few tens of nanometers to millimeters can be assembled out of magnetic nanoparticles. The long-range dipolar interaction between the nanoparticles determines the macroscopic magnetic response of the sample. Varying the size and shape of the regular elements as well as the distances between them offers the possibility to study magnetic coupling phenomena on different length scales. We study hierarchical arrangements of magnetite nanoparticles (Fe3O4) with diameters of about 20 nm by ferromagnetic resonance measurements. We demonstrate that the macroscopic properties of the structures are dominated by the assemblies of densely packed nanoparticles on the sub μm scale rather than by the interactions between these assemblies which are arranged on a grid with μm spacings or than by the macroscopic outer shape of the grid on the mm scale. The situation changes when the distances between the assemblies are reduced. We use ferromagnetic resonance (FMR) measurements to probe the magnetic interactions between the nanoparticles. Micro-magnetic simulations of the FMR spectra are carried out and allow us to relate the variation of the magnetic interactions with subtle lineshape changes of the spectra.