X-ray Absorption Spectroscopy Study on Sr2FeSi2O7, Ba2FeSi2O7

Abstract

In this paper, the electronic structure of two melilite compound Sr2FeSi2O7, Ba2FeSi2O7 was investigated by x-ray absorption spectroscopy. These compounds are consists of Si2O7 dimers linked by FeO4 tetrahedrons which have highly compressive distortion. However, there is still no precise understanding of ground state of electronic structure. These compressed tetrahedron crystal field environment have 2nd order spin-orbit coupling perturbation effect which splits the S=2 state into one singlet ground state and two doublet states. Spin-orbit coupling effect has an much smaller energy scale than the other dominant effects. So we performed polarization-dependent XAS measurements at the Fe L3 and L2 absorption edges to obtain linear dichroism which results from distortion. After that, atomic multiplet cluster calculation were used to analyze ground state energy splitting quantitatively. Therefore, we confirmed that single ion anisotropy difference between two samples closely related to structural distortion.