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Franck-Condon higher order lattice excitations in the LaFe(1-x)Cr(x)O3 (x=0, 0.1, 0.5, 0.9, 1.0) perovskites due to Fe-Cr charge transfer effects

Jakob Andreasson (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Joakim Holmlund (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Christopher S Knee (Institutionen för kemi- och bioteknik) ; Mikael Käll (Institutionen för teknisk fysik, Bionanofotonik) ; Lars Börjesson (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Stefan Naler ; Joakim Bäckström ; Michael Rübhausen ; A.K. Azad ; Sten G. Eriksson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
Physical Review B Vol. 75 (2007), p. 104302.
[Artikel, refereegranskad vetenskaplig]

First and higher order lattice excitiations in the B-site disordered perovskites LaFe(1-x)Cr(x)O3 (x = 0, 0.1, 0.5, 0.9, 1) and La(0.835)Sr(0.165)Fe(0.5)Cr(0.5)O(3-d) are investigated using temperature dependent and polarised inelastic light scattering [lambda = 515 nm (2.41 eV) and 676 nm (1.83 eV)] on oriented crystallites. A peak at approximately 2.4 eV in the imaginary part of the dielectric function of LaFe(0.5)Cr(0.5)O3 is assigned to a charge transfer from Fe 3+ (d5) to Cr 3+ (d3) ions and coupled the appearance of an intense Ag-like mode at approximately 700 cm-1 in the Raman data. This excitation is identified as a symmetric oxygen breathing mode activated by the Fe-Cr charge transfer through an orbital coupling mechanism. Higher order scattering (up to 7th order) of the intrinsic Raman active symmetric breathing mode is also explained by an orbital mediated, electron-phonon coupling, similar to the Franck-Condon effect observed in the Jahn-Teller active perovskite structured manganite LaMnO3. These results show that the Franck-Condon mechanism is a more common mechanism for resonant higher order scattering in solids than previously believed and propose the LaFe(1-x)Cr(x)O(3) system as a model system for electron-phonon coupling and higher order Raman scattering in solids.

Nyckelord: Perovskite, Raman, Higher order scattering, Charge transfer, Franck Condon



Denna post skapades 2007-05-16. Senast ändrad 2010-01-26.
CPL Pubid: 41738

 

Institutioner (Chalmers)

Institutionen för teknisk fysik, Kondenserade materiens fysik (1900-2015)
Institutionen för kemi- och bioteknik (2005-2014)
Institutionen för teknisk fysik, Bionanofotonik (2007-2015)
Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Fysik
Den kondenserade materiens fysik
Oorganisk kemi

Chalmers infrastruktur

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