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Open Access Publications from the University of California

Titanium 3d ferromagnetism with perpendicular anisotropy in defective anatase

  • Author(s): Stiller, M
  • N'Diaye, AT
  • Ohldag, H
  • Barzola-Quiquia, J
  • Esquinazi, PD
  • Amelal, T
  • Bundesmann, C
  • Spemann, D
  • Trautmann, M
  • Chassé, A
  • Hamed, HB
  • Adeagbo, WA
  • Hergert, W
  • et al.

This work focuses on the generation of ferromagnetism at the surface of anatase TiO2 films by low-energy ion irradiation. Controlled Ar+-ion irradiation resulted in a thin (∼10) nm ferromagnetic surface layer. The intrinsic origin and robustness of the magnetic order has been characterized by x-ray magnetic circular dichroism at room temperature revealing that a Ti band is spin-polarized. These results, together with density functional theory calculations, indicate that Ti vacancy-interstitial pairs are responsible for the magnetic order. Superconducting quantum interference device measurements show the existence of a perpendicular magnetic anisotropy and a low remanent magnetization. Magnetic force microscopy reveals that this low remanence is due to oppositely aligned magnetic domains with magnetization vectors normal to the main surface. The weak domain-wall pinning, the magnetic anisotropy, together with the simplicity of the preparation method, open up interesting possibilities for future applications. As an example, single domain patterns of ∼1μm width and several μm length can be easily prepared.

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