Explore the charge transfer and d-d excitation in perovskite manganite using 2p3d resonant inelastic X-ray scattering

Abstract

The resonant inelastic X-ray scattering (RIXS) is a powerful tool as a probe for the local electronic and magnetic structures and provides detailed knowledge on the 3d open shell valence state in solids and molecules. In this work, the electronic structure, charge transfer (CT), and d-d excitation studies in perovskite manganite: LaSr2Mn2O7 and La1.2(Ba, Ca)1.8Mn2O7 single crystals have been explored using X-ray absorption spectra (XAS) and RIXS. The incident photon energy was tuned in the vicinity of Mn L3,2 absorption edges (639.2, 650.2, and 660 eV) to induce the RIXS matrix. The various electronic structural parameters were estimated using the charge transfer multiplet (CTM) approach implemented in Cowan. It is observed that manganese ions are present in the predominant Mn3+/Mn4+ ground configurations. The TEY-XAS spectra showed a similarity in the surface electronic structure of both samples. However, the pre-edge shoulder, at XAS Mn L3 edge of La1.2(Ba, Ca)1.8Mn2O7 single crystal, is indicative of enhanced Mn3+ valence state and increase the Mn3+/Mn4+ concentration ratio. The ground and excited states of Mn3+ (3d4) in octahedral (Oh) local symmetry are 2T1 (1D) and 2E(2D) respectively. The ground state of trivalent Mn3+ (5D) exists with a high spin (HS) active state (|t2 g3 eg1>). We find that the separation between t2 g and eg states and the d–d excitation is primarily influenced by CF with a weak involvement of CT.