d-d Excitations in Bilayer Manganites Probed by Resonant Inelastic X-ray Scattering
Abstract
We report a high resolution resonant inelastic x-ray scattering investigation of the bilayer manganites La2-2xSr1+2xMn2O7 with x = 0.36 and 0.5. The momentum dependence along the crystallographic (110) direction for energy losses 1\,eV ≤ E ≤ 15\,eV has been measured in detail with the data analysis focusing on the energy loss region 1\,eV ≤ E ≤ 5\,eV, which includes a strong peak located at E ≈ 2\,eV. We observe a clear dispersion of up to 0.5\,eV in the measured q range, which is direct evidence of the non-local character of this excitation. Further, we found that the intensity in this low energy region strongly depends on both the reduced wave vector q = (h, h, 0), h = 0.1 - 0.5, and temperature, i.e. different ordered phases. Results can be explained via an intersite d-d charge transfer excitation, proposed for pseudo-cubic manganites, where the hopping rate is strongly increased (decreased) by ferromagnetic (antiferromagnetic) alignment of neighboring in-plane Mn ion core spins.