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dc.date.accessioned2018-01-05T15:11:53Z
dc.date.available2018-01-05T15:11:53Z
dc.date.created2002-01-13T14:14:19Z
dc.date.issued2001
dc.identifier.citationKaren, Pavel Woodward, Patrick M. Lindén, Johan Vogt, Tom Studer, Andrew Fischer, Peter . Verwey transition in mixed-valence TbBaFe2O5: Two attempts to order charges. Physical Review B. Condensed Matter and Materials Physics. 2001, 64(21), 214405/1-/14
dc.identifier.urihttp://hdl.handle.net/10852/59524
dc.description.abstractElectronic, magnetic, and structural phase transitions in nearly stoichiometric TbBaFe 2 O 5 + w ( 0.00 < w < 0.05 ) have been investigated. At high temperatures this compound is a paramagnetic, mixed-valence (Fe 2 . 5 + ) conductor with identical square-pyramidal coordinations at all iron atoms. Upon cooling below TN=450 K , an antiferromagnetic (AFM) spin order appears, accompanied by a magnetostrictive orthorhombic distortion. At lower temperatures the increasing distortion sets the frame for a first attempt to order charges. Mössbauer spectroscopy shows that one squeezed and one expanded square pyramid appear with different orientations of their magnetic and electric field tensors, each centered by its own mixed-valence iron state, one Fe 2 . 5 + ε , the other Fe 2.5 − ε . The lattice retains its distortion, but a small, structurally homogeneous, and continuous increase in volume is experienced. At somewhat lower temperature (TV) a discontinuous increase of the orthorhombic distortion occurs, marking the second attempt to order charges, now with the classical symptoms of the Verwey transition: a large change in volume, entropy, and electrical conductivity. Below TV, a normal Fe 3 + high-spin state in a symmetrical square-pyramidal coordination appears, whereas Fe 2 + is distorted. The long-range order of this arrangement is solved from high-resolution powder neutron diffraction data. Rietveld refinements show that the charge-ordered spins have AFM interactions in all three directions (G type) whereas in the mixed-valence state a ferromagnetic (FM) interaction appears between the iron atoms facing each other across the Tb layer. This FM interaction is suggested to be essential for the appearance of the mixed-valence state via the double-exchange sharing of the Fe 2 + -originated electron. This also allows for the total ordered spin moment being unchanged at the Verwey transition, following one single Brillouin curve. Analogous cases are pointed out where the Verwey transition proceeds in a similar manner, also at the molecular level. © 2001 American Physical Societyen_US
dc.languageEN
dc.publisherAmerican Physical Society
dc.titleVerwey transition in mixed-valence TbBaFe2O5: Two attempts to order chargesen_US
dc.typeJournal articleen_US
dc.creator.authorKaren, Pavel
dc.creator.authorWoodward, Patrick M.
dc.creator.authorLindén, Johan
dc.creator.authorVogt, Tom
dc.creator.authorStuder, Andrew
dc.creator.authorFischer, Peter
cristin.unitcode185,15,12,0
cristin.unitnameKjemisk institutt
cristin.ispublishedtrue
cristin.fulltextoriginal
cristin.qualitycode2
dc.identifier.cristin438698
dc.identifier.bibliographiccitationinfo:ofi/fmt:kev:mtx:ctx&ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Physical Review B. Condensed Matter and Materials Physics&rft.volume=64&rft.spage=214405/1&rft.date=2001
dc.identifier.jtitlePhysical Review B. Condensed Matter and Materials Physics
dc.identifier.volume64
dc.identifier.issue21
dc.identifier.startpage214405/1
dc.identifier.endpage/14
dc.identifier.doihttp://dx.doi.org/10.1103/PhysRevB.64.214405
dc.identifier.urnURN:NBN:no-62216
dc.type.documentTidsskriftartikkelen_US
dc.type.peerreviewedPeer reviewed
dc.source.issn1098-0121
dc.identifier.fulltextFulltext https://www.duo.uio.no/bitstream/handle/10852/59524/2/2001%2Btb.pdf
dc.type.versionPublishedVersion


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