title: Size dependent structural and magnetic properties of FeO-Fe3O4 nanoparticles.
abstract: The magnetic properties of monodisperse FeO-Fe3O4 nanoparticles with different mean sizes and volume fractions of FeO synthesized via decomposition of iron oleate were correlated to their crystallographic and phase compositional features by exploiting high resolution transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy and field and zero field cooled magnetization measurements. A model describing the phase transformation from a pure Fe3O4 phase to a mixture of Fe3O4, FeO and interfacial FeO-Fe3O4 phases as the particle size increases was established. The reduced magnetic moment in FeO-Fe3O4 nanoparticles was attributed to the presence of differently oriented Fe3O4 crystalline domains in the outer layers and paramagnetic FeO phase. The exchange bias energy, dominating magnetization reversal mechanism and superparamagnetic blocking temperature in FeO-Fe3O4 nanoparticles depend strongly on the relative volume fractions of FeO and the interfacial phase.
authors.affiliation: TU Braunschweig, Institute of Electrical Measurement and Fundamental Electrical Engineering, Hans-Sommer-St. 66, 38106 Braunschweig, Germany. a.lak@tu-bs.de f.ludwig@tu-bs.de.
authors.forename: Aidin
authors.initials: A
authors.lastname: Lak
authors.forename: Mathias
authors.initials: M
authors.lastname: Kraken
authors.forename: Frank
authors.initials: F
authors.lastname: Ludwig
authors.forename: Andreas
authors.initials: A
authors.lastname: Kornowski
authors.forename: Dietmar
authors.initials: D
authors.lastname: Eberbeck
authors.forename: Sibylle
authors.initials: S
authors.lastname: Sievers
authors.forename: F J
authors.initials: FJ
authors.lastname: Litterst
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
authors.forename: Meinhard
authors.initials: M
authors.lastname: Schilling