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

摘要: First and higher order lattice excitations in the B-site disordered perovskites LaFe1-xCrxO3 (x=0, 0.1, 0.5, 0.9, 1) La0.835Sr0.165Fe0.5Cr0.5O3-delta are investigated using temperature dependent polarized inelastic light scattering [lambda=515 nm (2.41 eV) 676 (1.83 eV)] on oriented crystallites. A peak at approximately 2.4 eV imaginary part of dielectric function LaFe0.5Cr0.5O3 is assigned to a charge transfer from Fe3+ (d(5)) Cr3+ (d(3)) ions, coupled with appearance an intense A(g)-like mode 700 cm(-1) Raman data. This excitation identified as symmetric oxygen breathing activated by Fe-Cr through orbital coupling mechanism. Higher (up seventh order) intrinsic active also explained orbital-mediated electron-phonon coupling, similar Franck-Condon effect observed Jahn-Teller active-perovskite-structured manganite LaMaO(3). These results show that mechanism more common for resonant solids than previously believed propose system model solids.