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Electron-phonon int...
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Andreasson, Jakob,1975Uppsala universitet,Institutionen för cell- och molekylärbiologi,Chalmers tekniska högskola,Chalmers University of Technology
(författare)
Electron-phonon interactions in perovskites containing Fe and Cr studied by Raman scattering using oxygen-isotope and cation substitution
- Artikel/kapitelEngelska2008
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Nummerbeteckningar
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LIBRIS-ID:oai:DiVA.org:uu-137357
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https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-137357URI
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https://doi.org/10.1103/PhysRevB.78.235103DOI
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https://research.chalmers.se/publication/81116URI
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https://gup.ub.gu.se/publication/81116URI
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Språk:engelska
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Sammanfattning på:engelska
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Ämneskategori:ref swepub-contenttype
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Ämneskategori:art swepub-publicationtype
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We use temperature-dependent inelastic light scattering to study the origin of the strong multiphonon scattering of a local oxygen breathing mode present in the mixed B-site orthorhombic (space group Pnma) perovskite LaFe0.5Cr0.5O3 but absent in isostructural LaFeO3 and LaCrO3. It is seen that the multiphonon scattering is critically sensitive to the presence of both Fe and Cr ions on the B site. These results support our interpretation that the multiphonon scattering is activated by local electron-phonon interactions according to the Franck-Condon picture following an Fe-Cr charge transfer. Further, O-18 substitution is performed on the x=0, 0.04, and 0.5 compounds and clearly shows that all modes appearing above the first-order phonon-scattering region in these compounds originate from higher-order oxygen stretching vibrations. In particular this is the case for the strong second-order scattering dominating the scattering response in LaFeO3. Accordingly we propose that these modes are generated by infrared-active longitudinal optical (IR LO) two-phonon and combination scattering activated by Frohlich interaction. For x=0.02 and 0.04 the characteristic IR LO two-phonon and Franck-Condon multiphonon-scattering profiles mix. We also study the influence of isovalent cation substitution and Sr doping in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) and La1-ySryFe0.5Cr0.5O3-delta (y=0, 0.16, and 0.5) on the strong electron-phonon coupling present in LaFe0.5Cr0.5O3. The Franck-Condon effect in LaFe0.5Cr0.5O3, is not significantly affected by isovalent A-site substitution, despite the increasing orthorhombic distortion associated with decreasing A-site ionic radii. On the contrary, aliovalent Sr doping causes a rapid decrease in the Franck-Condon scattering. This shows that the strong electron-phonon coupling in these compounds is highly sensitive to local lattice and electronic decoherence but insensitive to global lattice distortions. Finally, a preliminary assignment of the A(g) and B-2g phonon modes in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) is made based on the present observations and published results for LaCrO3 and AMnO(3). The modes associated with oxygen octahedral tilt and bending vibrations are heavily influenced by the magnitude of the orthorhombic distortion.
Ämnesord och genrebeteckningar
Biuppslag (personer, institutioner, konferenser, titlar ...)
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Holmlund, Joakim,1968Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)gu98joho
(författare)
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Rauer, Ralf,1974Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)rauer
(författare)
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Käll, Mikael,1963Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)kall
(författare)
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Börjesson, Lars,1957Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)lborje
(författare)
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Knee, Christopher,1973Gothenburg University,Göteborgs universitet,Institutionen för kemi,Department of Chemistry(Swepub:cth)knee
(författare)
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Eriksson, Annika,1975Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)anneka
(författare)
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Eriksson, Sten,1958Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)stene
(författare)
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Ruebhausen, Michael
(författare)
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Chaudhury, Rajit P.
(författare)
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Uppsala universitetInstitutionen för cell- och molekylärbiologi
(creator_code:org_t)
Sammanhörande titlar
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Ingår i:Physical Review B. Condensed Matter and Materials Physics78:23, s. 235103-1098-01211550-235X2469-99502469-9969
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Andreasson, Jako ...
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Holmlund, Joakim ...
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Rauer, Ralf, 197 ...
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Käll, Mikael, 19 ...
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Börjesson, Lars, ...
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Knee, Christophe ...
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Eriksson, Annika ...
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