Surface anisotropy change of CoFe2O4 nanoparticles depending on thickness of coated SiO2 shell

  • Mustafa Coşkun
  • Musa Mutlu Can
  • Özlem Duyar Coşkun
  • Mustafa Korkmaz
  • Tezer Fırat
Research Paper


We systematically investigated the effective surface anisotropy of CoFe2O4 nanoparticles dependant on the thickness of SiO2 shell. XRD (X-ray powder diffraction) patterns and TEM (transmission electron microscopy) micrographs were used to investigate the structure of particles and thickness of SiO2 shell, respectively. The thicknesses of SiO2 shell with 5.41 nm on CoFe2O4 nanoparticles were increased up to 14.04 ± 0.05 nm by changing the amount of added TEOS by, 0.10, 0.25, 0.50, 1.00, 1.50, and 2.50 mL. The increase of the SiO2 thickness shell decreased the effective anisotropy due to decline the effectiveness of the dipolar magnetostatic interactions, determined from Vogel–Fulcher equation, between the particles. The declines in the Keff values stabled at around 3.76 ± 0.11 × 105 J/m3 for TEOS amount higher than 1.5 mL.


Dipolar interaction Magnetic anisotropy Ferrite nanoparticles SiO2 shell 


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Mustafa Coşkun
    • 1
    • 2
  • Musa Mutlu Can
    • 3
  • Özlem Duyar Coşkun
    • 1
  • Mustafa Korkmaz
    • 1
  • Tezer Fırat
    • 1
  1. 1.Department of Physics EngineeringHacettepe UniversityAnkaraTurkey
  2. 2.Ministry of Energy and Natural ResourcesAnkaraTurkey
  3. 3.Faculty of Engineering and Natural SciencesNanotechnology Research and Application Center, Sabancı UniversityIstanbulTurkey

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