X-Ray Absorption Spectroscopic Study of New High-TcSuperconducting Intercalation Compound of (HgX2)0,5Bi2Sr2CaCu2Oy(X = Br, I)

Abstract

We have systematically performed X-ray absorption spectroscopic (XAS) studies on the new mercuric halide intercalated superconductors, (HgX 2 ) 0.5 Bi 2 Sr 2 CaCu 2 O y with X = Br and I, in order to investigate the electronic and crystal structures of these compounds. According to the I L 1- and Br K-edge X-ray absorption near edge structure (XANES) spectroscopic analyses, it is found that a small amount of electron is transferred from the intercalant HgX 2 to the host lattice, resulting in the negatively charged state of (HgX 2 ) δ- . The Cu K-edge extended X-ray absorption fine structure (EXAFS) analysis reveals that the bond distance or (Cu-O axial ) is slightly shortened upon intercalation, reflecting the oxidation of CuO 2 layer, which is well consistent with the I L 1- and Br K-edge XANES results. On the other hand, the present Hg L III -edge EXAFS results indicate that the metal is coordinated with two bromide or iodide ligands with bond length of 2.46 A for the HgBr 2 -intercalate and 2.65 A for the HgI 2 -one, respectively. This is the first example of linear molecular salt of HgX 2 stabilized in the solid lattice.