title: Oxygen vacancy induced room temperature ferromagnetism in Pr-doped CeO2 thin films on silicon.
abstract: Integration of functional oxides on Si substrates could open a pathway to integrate diverse devices on Si-based technology. Oxygen vacancies (Vo(··)) can strongly affect solid state properties of oxides, including the room temperature ferromagnetism (RTFM) in diluted magnetic oxides. Here, we report a systematical study on the RTFM of oxygen vacancy engineered (by Pr(3+) doping) CeO2 epitaxial thin films on Si substrates. High quality, mixed single crystalline Ce1-xPrxO2-δ (x = 0-1) solid solution films were obtained. The Ce ions in CeO2 with a fluorite structure show a Ce(4+)-dominant valence state in all films. The local crystal structures of the films were analyzed in detail. Pr doping creates both Vo(··) and PrO8-complex defects in CeO2 and their relative concentrations vary with the Pr-doping level. The RTFM properties of the films reveal a strong dependence on the relative Vo(··) concentration. The RTFM in the films initially increases with higher Pr-doping levels due to the increase of the F(+) center (Vo(··) with one occupied electron) concentration and completely disappears when x > 0.2, where the magnetic polaron concentration is considered to decline below the percolation threshold, thus long-range FM order can no longer be established. We thus demonstrate the possibility to directly grow RTFM Pr-doped CeO2 films on Si substrates, which can be an interesting candidate for potential magneto-optic or spintronic device applications.
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Gang
authors.initials: G
authors.lastname: Niu
authors.forename: Erwin
authors.initials: E
authors.lastname: Hildebrandt
authors.forename: Markus Andreas
authors.initials: MA
authors.lastname: Schubert
authors.forename: Federico
authors.initials: F
authors.lastname: Boscherini
authors.forename: Marvin Hartwig
authors.initials: MH
authors.lastname: Zoellner
authors.forename: Lambert
authors.initials: L
authors.lastname: Alff
authors.forename: Damian
authors.initials: D
authors.lastname: Walczyk
authors.forename: Peter
authors.initials: P
authors.lastname: Zaumseil
authors.forename: Ioan
authors.initials: I
authors.lastname: Costina
authors.forename: Henrik
authors.initials: H
authors.lastname: Wilkens
authors.forename: Thomas
authors.initials: T
authors.lastname: Schroeder
keywords: doping; ferromagnetism; oxides; oxygen vacancies; thin films