2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals

Bertrand Faure, Erik Wetterskog, Klas Gunnarsson, Elisabeth Josten, Raphaël P. Hermann, Thomas Brückel, Jens Wenzel Andreasen, Florian Meneau, Mathias Meyer, Alexander Lyubartsev, Lennart Bergström, German Salazar-Alvarez, Peter Svedlindh

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Abstract

The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe2O3 spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array. The 2D to 3D transition in the magnetic properties is mainly driven by a change in the orientation of the magnetic vortex states with increasing thickness, becoming more isotropic as the thickness of the array increases. Magnetic anisotropy prevents long-range ferromagnetic order from being established at low temperature and the nanoparticle magnetic moments instead freeze along directions defined by the distribution of easy magnetization directions. © 2013 The Royal Society of Chemistry.
Original languageEnglish
JournalNanoscale
Volume5
Issue number3
Pages (from-to)953-960
ISSN2040-3364
DOIs
Publication statusPublished - 2013

Keywords

  • Ferromagnetic materials
  • Ferromagnetism
  • Iron oxides
  • Magnetic anisotropy
  • Magnetic moments
  • Monte Carlo methods
  • Nanomagnetics
  • Nanoparticles
  • Saturation magnetization
  • Scanning electron microscopy
  • Three dimensional computer graphics

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