New route to estimate the Mott-Hubbard and charge transfer parameters: An optical and x-ray absorption studies

Abstract

X-ray absorption spectroscopy (XAS) and optical absorption spectroscopy (OAS) measurements have been performed on polycrystalline samples of PrFeO3+δ sintered at different temperatures. XAS measurements carried out at Fe K-edge confirms the increase in the concentration of Fe4+ ions in PrFeO3+δ with sintering temperature (TS). The optical band gap (Eg) of these samples appears to be correlated with that of the bandwidth (dBW-Fe-3d) of the “Fe-3d” orbital. The values of dBW-Fe-3d have been estimated from XAS data collected at Fe L3-edge. The increase in the dBW-Fe-3d is attributed to be due to the splitting of Fe-3d (t2g)III and Fe-3d (eg)II states due to the presence of Fe4+ Jahn-Teller ions. The OAS spectral analysis suggests that the band gap decreases systematically with TS. The relative intensity of d-d transition has been found to scale with the concentration of Fe4+ ions and the width of the said d-d transition seems to be correlated with dBW-Fe-3d. Using the estimated values of ‘Eg’ and d-bandwidth, the value of charge transfer parameter ‘Δ’ has been estimated. The obtained value of Δ is used to simulate the band gap of PrFeO3 using density functional theoretical analysis. Thus, using the combination of x-ray absorption and optical spectroscopies we have demonstrated the new way to investigate and analyse the electronic structure of strongly correlated electron systems.