Structural, electronic, and magnetic properties of nanometer-sized iron-oxide atomic clusters: Comparison between GGA and GGA+U approaches

K. Palotás, Antonis N. Andriotis, Alexandros Lappas

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We perform spin-polarized density-functional theory simulations within the generalized gradient approximation (GGA) and GGA+U method on nanometer-sized iron-oxide atomic clusters in different stoichiometries. By comparing total energies of structures with different symmetries and selected collinear magnetic configurations we find that low symmetry and, in general, ferrimagnetic structures exhibiting low total magnetic moment are energetically favorable. For the oxygen-rich Fe25 O30 cluster we obtain a cagelike geometry with a few ions within the cage that seem to stabilize the structure. Considering the Fe33 O32 cluster of nanometer-size we propose the formation of a rocksalt type structure, which is characteristic of bulk FeO. Based on data of iron d shell electron occupancies, we exclude double exchange from possible magnetic interactions between iron ions, and we point to a competition between direct exchange and superexchange, where the dominant interaction is determined by the cluster topology. For the smaller Fe13 O8 cluster we find ferromagnetic energetically favorable geometries of lower symmetry than previously reported. Our results demonstrate the importance of going beyond GGA, in particular, physical properties obtained within GGA+U description are found to be remarkably different from those using GGA. In order to confirm our theoretical predictions, cluster experiments in this size regime are desirable.

Original languageEnglish
Article number075403
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume81
Issue number7
DOIs
Publication statusPublished - Feb 2 2010

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atomic clusters
Iron oxides
iron oxides
Electronic properties
Structural properties
Magnetic properties
Iron
Ions
magnetic properties
gradients
Geometry
Magnetic moments
approximation
electronics
Stoichiometry
Density functional theory
Ion exchange
Physical properties
Topology
Oxygen

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Structural, electronic, and magnetic properties of nanometer-sized iron-oxide atomic clusters : Comparison between GGA and GGA+U approaches. / Palotás, K.; Andriotis, Antonis N.; Lappas, Alexandros.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 81, No. 7, 075403, 02.02.2010.

Research output: Contribution to journalArticle

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