Growth and characterization of ultrathin cobalt ferrite films on Pt(111)

CoFe2O4 thin films (5 nm and 20 nm thick) were grown by oxygen assisted molecular beam epitaxy on Pt(111) at 523 K and subsequently annealed at 773 K in vacuum or oxygen. They were characterized in-situ using Auger Electron Spectroscopy, Low-Energy Electron Diffraction, Scanning Tunneling Microscopy...

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Veröffentlicht in:Applied surface science 2022-06, Vol.586, p.152672, Article 152672
Hauptverfasser: Soria, G.D., Freindl, K., Prieto, J.E., Quesada, A., de la Figuera, J., Spiridis, N., Korecki, J., Marco, J.F.
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Sprache:eng
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Zusammenfassung:CoFe2O4 thin films (5 nm and 20 nm thick) were grown by oxygen assisted molecular beam epitaxy on Pt(111) at 523 K and subsequently annealed at 773 K in vacuum or oxygen. They were characterized in-situ using Auger Electron Spectroscopy, Low-Energy Electron Diffraction, Scanning Tunneling Microscopy and Conversion Electron Mössbauer Spectroscopy. The as-grown films were composed of small, nanometric grains. Annealing of the films produced an increase in the grain size and gave rise to magnetic order at room temperature, although with a fraction of the films remaining in the paramagnetic state. Annealing also induced cobalt segregation to the surface of the thicker films. The measured Mössbauer spectra at low temperature were indicative of cobalt ferrite, the both films showing very similar hyperfine patterns. Annealing in oxygen or vacuum affected the cationic distribution, which was closer to that expected for an inverse spinel in the case of annealing in an oxygen atmosphere. [Display omitted] •Cobalt ferrite ultrathin films were synthesized by molecular beam epitaxy on Pt(111).•In-situ growth and characterization of the films.•The as-grown thinner film presented a higher magnetic ordering than the thicker one.•Annealing promoted the cationic distribution of an inverse spinel.•Mössbauer spectroscopy revealed the cationic distribution at each step.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2022.152672