• English
    • Norsk
  • English 
    • English
    • Norsk
  • Administration
View Item 
  •   Home
  • Øvrige samlinger
  • Høstingsarkiver
  • CRIStin høstingsarkiv
  • View Item
  •   Home
  • Øvrige samlinger
  • Høstingsarkiver
  • CRIStin høstingsarkiv
  • View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.

Verwey transition in mixed-valence TbBaFe2O5: Two attempts to order charges

Karen, Pavel; Woodward, Patrick M.; Lindén, Johan; Vogt, Tom; Studer, Andrew; Fischer, Peter
Journal article; PublishedVersion; Peer reviewed
View/Open
2001+tb.pdf (1.025Mb)
Year
2001
Permanent link
http://urn.nb.no/URN:NBN:no-62216

CRIStin
438698

Metadata
Show metadata
Appears in the following Collection
  • Kjemisk institutt [843]
  • CRIStin høstingsarkiv [15898]
Original version
Physical Review B. Condensed Matter and Materials Physics. 2001, 64 (21), 214405/1-/14, DOI: http://dx.doi.org/10.1103/PhysRevB.64.214405
Abstract
Electronic, 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 Society
 
Responsible for this website 
University of Oslo Library


Contact Us 
duo-hjelp@ub.uio.no


Privacy policy
 

 

For students / employeesSubmit master thesisAccess to restricted material

Browse

All of DUOCommunities & CollectionsBy Issue DateAuthorsTitlesThis CollectionBy Issue DateAuthorsTitles

For library staff

Login
RSS Feeds
 
Responsible for this website 
University of Oslo Library


Contact Us 
duo-hjelp@ub.uio.no


Privacy policy