Valence states of bismuth and thallium in superconducting cuprates: a Bi–L₃ and Tl–L₃ X-ray absorption spectroscopic study

Abstract

Based on a Bi–L₃ edge X-ray absorption spectroscopic study of superconducting bismuth cuprates and model Bi compounds, it is shown that Bi is essentially in the 3+ state in the cuprates. Tl–L₃ absorption edge studies a number of thallium cuprate superconductors along with those of model compounds show some evidence for the occupancy of the Tl-6s band, but Tl³⁺ is the prepondarant species. Cu K-edge studies of the thallium cuprates show that Cu is essentially in the 2+ state.