Search for orbitons in LaMnO3, YTiO3 and KCuF3 using high-resolution inelastic x-ray scattering

Orbital excitations have been sought in three systems, LaMnO3, KCuF3 andYTiO3, using high-resolution inelastic x-ray scattering, with an energy resolution of 6 meV. Motivated by the recent Raman scattering result of Saitoh et al (2001 Nature 410 180), we measured the energy transfer spectra of LaMnO3 in the energy range up to 200 meV. We did not find any signal above background that could be associated with orbiton excitations. Since significant interaction between the spin and orbital degrees of freedom is expected in KCuF3 andYTiO3, energy spectra were measured above and below the respective magnetic ordering temperature. We were not able to detect any change in the excitation spectra due to the magnetic ordering temperature of these materials. We discuss the implications of the experimental findings and estimate an upper bound on the orbiton x-ray cross-section. 6 Author to whom any correspondence should be addressed. New Journal of Physics 6 (2004) 161 PII: S1367-2630(04)84752-9 1367-2630/04/010161+13$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft 2 DEUTSCHE PHYSIKALISCHE GESELLSCHAFT