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10-23 ICQMS seminar: Size effects on the local magnetism of an isolated impurity in metals

创建日期 2018/10/22 永乐   浏览次数  59   返回    
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报告题目(Title):Size effects on the local magnetism of an isolated impurity in metals

报 告 人(Speaker):Susanta Kumar Mohanta(Government College of Engineering Kalahandi,India)

报告时间(Time):2018年10月23日(周二) 上午 9:00

报告地点(Place):校本部E106


邀请人(inviter): 任伟

报告摘要(Abstract):Properties of solids, whether structural, mechanical, optical, electrical, magnetic or transport, are decided to a great extent by the behaviour of individual constituent atoms or ions, and their immediate surroundings, in the solid environment. A few familiar examples of materials influenced by the local atomic behaviour are ferromagnets, antiferromagnets, superconductors etc. As an example, the magnetic moment of a magnetic atom in a metallic solid may survive fully, partially or not at all, depending on its interactions with the conduction electrons. Thus, the study of local atomic behaviour occupies a key position in the central theme of the current experimental and theoretical research in condensed matter physics. The precise observation and understanding of the local atomic properties, however, requires a microscopic investigation at the atomic length and short time (ns) scales. For this, one needs to have the local information coming out directly from the atom under investigation. This can be accomplished if the nucleus of the atom emits γ-rays. The angular anisotropic distribution of the intensity of γ-rays is perturbed due to the hyperfine interactions of the nuclear electric quadrupole and/or magnetic moments with the local crystal electromagnetic fields, like electric field gradient (EFG) and the magnetic hyperfine field (Bhf). This perturbation can be detected with the techniques named perturbed angular correlation (PAC).
In this talk, I will highlight few of our recent results on the size effect on the local magnetism of an isolated impurity in few metals like, Nb, Pb, Ta, Hexagonal-Ag and one strongly correlated system CePd3 . The results show clear indication of localized behaviour as the grain size decreases compared to the bulk. Although the results are non-universal, we are trying to understand and quantify the general trend observed through ab initio band structure computation. Here. I would like to emphasize on the long standing problem, that needs to be addressed in today’s context.

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