HRTEM and EELS studies of L10-ordered FePt nano-clusters on MgO films prepared below 673 K

Shunsuke Fukami, Akichika Ohno, Nobuo Tanaka

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11 Citations (Scopus)

Abstract

Three kinds of FePt-MgO granular films were prepared by a vacuum successive deposition of MgO, Pt, Fe and MgO on a cleaved surface of sodium chloride below 673 K. Their microstructures, electronic structures and magnetic properties were studied by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS) and measurement with a superconducting quantum interference device (SQUID) magnetometer. The TEM observations and selected area electron diffraction patterns revealed that the samples mainly consist of few nm-sized FePt clusters embedded in MgO films with L10-ordered structure and c-axis perpendicular to the film surface. Size effect on the stability of L10 phase in the FePt nano-clusters was directly observed in [MgO/Fe(0.38nm)/Pt(0.30nm)/MgO] and the critical size of the transition from L10 to Al phase was estimated as around 2 nm, that can be considered as smaller than effective size for the transition from ferromagnetism to superparamagnetism. Coercivity of [MgO/Fe(1.0nm)/Pt(0.8nm)/MgO] was 1.2 × 105 A/m. The Fe-L 2,3 white-line ratios of the present samples measured by EELS were about 4.0, independently on the incident direction of electron beam. The higher white-line ratio may be attributed to their high-spin state by a change of 3d-band structure owing to the hybridization of d-bands between Fe and Pt atoms.

Original languageEnglish
Pages (from-to)2012-2017
Number of pages6
JournalMaterials Transactions
Volume45
Issue number7
DOIs
Publication statusPublished - 2004 Jul

Keywords

  • Electron energy-loss spectroscopy
  • High-resolution transmission electron microscopy
  • Low temperature preparation
  • Magnesium oxide
  • Nano-cluster
  • Perpendicular magnetic recording media
  • Size-effect
  • White-line ratio

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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