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王荣明

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期刊论文

FePt Icosahedra with Magnetic Cores and Catalytic Shells

王荣明Rongming Wang*‡ Olga Dmitrieva§ Michael Farle§ Gunter Dumpich§ Mehmet Acet§ Sergio Mejia-Rosales‖Eduardo Perez-Tijerina‖ Miguel Jose Yacaman and Christian Kisielowski‡

J. Phys. Chem. C 2009, 113, 4395-4400,-0001,():

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摘要/描述

Surprisingly oxidation resistant icosahedral FePt nanoparticles showing hard-magnetic properties have beenfabricated by an inert-gas condensation method with in-flight annealing. High-resolution transmission electronmicroscopy (HRTEM) images with sub-Angstrom resolution of the nanoparticle have been obtained withfocal series reconstruction, revealing noncrystalline nature of the nanoparticle. Digital dark-field methodcombined with structure reconstruction as well as HRTEM simulations reveal that these nanoparticles haveicosahedral structure with shell periodicity. Localized lattice relaxations have been studied by extracting theposition of individual atomic columns with a precision of about (0.002 nm. The lattice spacings of (111)planes from the surface region to the center of the icosahedra are found to decrease exponentially with shellnumbers. Computational studies and energy-filtered transmission electron microscopy analyses suggest thata Pt-enriched surface layer is energetically favored and that site-specific vacancies are formed at the edges offacettes, which was experimentally observed. The presence of the Pt-enriched shell around an Fe/Pt coreexplains the environmental stability of the magnetic icosahedra and strongly reduces the exchange couplingbetween neighboring particles, thereby possibly providing the highest packing density for future magneticstorage media based on FePt nanoparticles.

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版权说明:以下全部内容由王荣明上传于   2009年03月24日 07时59分44秒,版权归本人所有。

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