FePt icosahedra with magnetic cores and catalytic shells

Rongming Wang, Olga Dmitrieva, Michael Farle, Dumpich Günter Dumpich, Mehmet Acet, Sergio Mejia-Rosales, Eduardo Perez-Tijerina, Miguel Jose Yacaman, Christian Kisielowski

Research output: Contribution to journalArticlepeer-review

72 Scopus citations

Abstract

Surprisingly oxidation resistant icosahedral FePt nanoparticles showing hard-magnetic properties have been fabricated by an inert-gas condensation method with in-flight annealing. High-resolution transmission electron microscopy (HRTEM) images with sub-Angstrom resolution of the nanoparticle have been obtained with focal series reconstruction, revealing noncrystalline nature of the nanoparticle. Digital dark-field method combined with structure reconstruction as well as HRTEM simulations reveal that these nanoparticles have icosahedral structure with shell periodicity. Localized lattice relaxations have been studied by extracting the position 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 shell numbers. Computational studies and energy-filtered transmission electron microscopy analyses suggest that a Pt-enriched surface layer is energetically favored and that site-specific vacancies are formed at the edges of facettes, which was experimentally observed. The presence of the Pt-enriched shell around an Fe/Pt core explains the environmental stability of the magnetic icosahedra and strongly reduces the exchange coupling between neighboring particles, thereby possibly providing the highest packing density for future magnetic storage media based on FePt nanoparticles.

Original languageEnglish (US)
Pages (from-to)4395-4400
Number of pages6
JournalJournal of Physical Chemistry C
Volume113
Issue number11
DOIs
StatePublished - Mar 19 2009
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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