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dc.contributor.authorCOEY, JOHNen
dc.contributor.authorVENKATESAN, MUNUSWAMYen
dc.contributor.authorSTAMENOV, PLAMENen
dc.date.accessioned2010-06-28T16:27:14Z
dc.date.available2010-06-28T16:27:14Z
dc.date.issued2010en
dc.date.submitted2010en
dc.identifier.citationJ M D Coey, P Stamenov, R D Gunning, M Venkatesan and K Paul, Ferromagnetism in defect-ridden oxides and related materials, New Journal of Physics, 12, 2010, 053025 -en
dc.identifier.otherYen
dc.identifier.urihttp://hdl.handle.net/2262/40210
dc.descriptionPUBLISHEDen
dc.description.abstractThe existence of high-temperature ferromagnetism in thin films and nanoparticles of oxides containing small quantities of magnetic dopants remains controversial. Some regard these materials as dilute magnetic semiconductors, while others think they are ferromagnetic only because the magnetic dopants form secondary ferromagnetic impurity phases such as cobalt metal or magnetite. There are also reports in d0 systems and other defective oxides that contain no magnetic ions. Here, we investigate TiO2 (rutile) containing 1?5% of iron cations and find that the room temperature ferromagnetism of films prepared by pulsed-laser deposition is not due to magnetic ordering of the iron. The films are neither dilute magnetic semiconductors nor hosts to an iron-based ferromagnetic impurity phase. A new model is developed for defect-related ferromagnetism, which involves a spin-split defect band populated by charge transfer from a proximate charge reservoir?in the present case a mixture of Fe2 + and Fe3 + ions in the oxide lattice. The phase diagram for the model shows how inhomogeneous Stoner ferromagnetism depends on the total number of electrons Ntot, the Stoner exchange integral I and the defect bandwidth W; the band occupancy is governed by the d?d Coulomb interaction U. There are regions of ferromagnetic metal, half-metal and insulator as well as non-magnetic metal and insulator. A characteristic feature of the high-temperature Stoner magnetism is an anhysteretic magnetization curve, which is practically temperature independent below room temperature. This is related to a wandering ferromagnetic axis, which is determined by local dipole fields. The magnetization is limited by the defect concentration, not by the 3d doping. Only 1?2% of the volume of the films is magnetically ordered.en
dc.description.sponsorshipThis work was supported by Science Foundation Ireland as part of the CINSE and MANSE programs. K P was supported by the SFI EUREKA scheme.en
dc.format.extent053025en
dc.language.isoenen
dc.relation.ispartofseriesNew Journal of Physicsen
dc.relation.ispartofseries12en
dc.rightsYen
dc.subjectPhysicsen
dc.subjectFerromagnetismen
dc.titleFerromagnetism in defect-ridden oxides and related materialsen
dc.typeJournal Articleen
dc.contributor.sponsorScience Foundation Ireland (SFI)en
dc.type.supercollectionscholarly_publicationsen
dc.type.supercollectionrefereed_publicationsen
dc.identifier.peoplefinderurlhttp://people.tcd.ie/jcoeyen
dc.identifier.peoplefinderurlhttp://people.tcd.ie/stamenpen
dc.identifier.peoplefinderurlhttp://people.tcd.ie/venkatemen
dc.identifier.rssinternalid67338en
dc.subject.TCDThemeNanoscience & Materialsen
dc.identifier.rssurihttp://dx.doi.org/10.1088/1367-2630/12/5/053025en


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