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
Journal article, 2007

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.

Higher order scattering


Franck Condon

Charge transfer



Jakob Andreasson

Chalmers, Applied Physics, Condensed Matter Physics

Joakim Holmlund

Chalmers, Applied Physics, Condensed Matter Physics

Christopher Knee

Chalmers, Chemical and Biological Engineering

Mikael Käll

Chalmers, Applied Physics, Bionanophotonics

Lars Börjesson

Chalmers, Applied Physics, Condensed Matter Physics

Stefan Naler

Joakim Bäckström

Michael Rübhausen

A.K. Azad

Sten Eriksson

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Physical Review B

Vol. 75 104302-

Subject Categories

Inorganic Chemistry

Physical Sciences

Condensed Matter Physics



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