Characterization of superparamagnetic "core-shell" nanoparticles and monitoring their anisotropic phase transition to ferromagnetic "solid solution" nanoalloys

Jong Il Park, Min Gyu Kim, Young Wook Jun, Jae Sung Lee, Woo Ram Lee, Jinwoo Cheon

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Abstract

The structure, magnetism, and phase transition of core-shell type CoPt nanoparticles en route to solid solution alloy nanostructures are systematically investigated. The characterization of CocorePtshell nanoparticles obtained by a "redox transmetalation" process by transmission electron microscopy (TEM) and, in particular, X-ray absorption spectroscopy (XAS) provides clear evidence for the existence of a core-shell type bimetallic interfacial structure. Nanoscale phase transitions of the CocorePtshell structures toward c-axis compressed face-centered tetragonal (fct) solid solution alloy CoPt nanoparticles are monitored at various stages of a thermally induced annealing process and the obtained fct nanoalloys show a large enhancement of their magnetic properties with ferromagnetism. The relationship between the nanostructures and their magnetic properties is in part elucidated through the use of XAS as a critical analytical tool.

Original languageEnglish
Pages (from-to)9072-9078
Number of pages7
JournalJournal of the American Chemical Society
Volume126
Issue number29
DOIs
Publication statusPublished - 2004 Jul 28

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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