title: Reversed ageing of Fe3O4 nanoparticles by hydrogen plasma.
abstract: Magnetite (Fe3O4) nanoparticles suffer from severe ageing effects when exposed to air even when they are dispersed in a solvent limiting their applications. In this work, we show that this ageing can be fully reversed by a hydrogen plasma treatment. By x-ray absorption spectroscopy and its associated magnetic circular dichroism, the electronic structure and magnetic properties were studied before and after the plasma treatment and compared to results of freshly prepared magnetite nanoparticles. While aged magnetite nanoparticles exhibit a more γ-Fe2O3 like behaviour, the hydrogen plasma yields pure Fe3O4 nanoparticles. Monitoring the temperature dependence of the intra-atomic spin dipole contribution to the dichroic spectra gives evidence that the structural, electronic and magnetic properties of plasma treated magnetite nanoparticles can outperform the ones of the freshly prepared batch.
authors.affiliation: Peter-Grünberg-Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany.|Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Schmitz-Antoniak
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str.15, 12489 Berlin, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Schmitz
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Warland
authors.affiliation: Peter-Grünberg-Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Svechkina
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany.
authors.forename: Soma
authors.initials: S
authors.lastname: Salamon
authors.affiliation: Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
authors.forename: Cinthia
authors.initials: C
authors.lastname: Piamonteze
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Wende