Superconductivity, X-ray structure and non stoichiometry of HgBa2CuO4+δ

Abstract Single crystals and pure single phase powder material of HgBa 2 CuO 4+δ (Hg-1201) have been obtained with the same single step synthesis technique under normal pressure conditions used to grow single crystals of HgBa 2 Ca 2 Cu 3 O 8+δ (Hg-1223) [1]. X-rays structural investigations carried out on single crystals show no substitutional defects at the mercury site, in particular no mixed occupancy of copper, in contrast to the case of Hg-1223. Excess oxygen content appears to be present only in the basal plane at the interstitial site 1/2 1/2 0. The domain of δ values has been investigated by thermogravimetry, allowing to derive Tc versus δ without resorting to high oxygen pressures in the overdoped regime. We present both transverse and longitudinal magnetization measurements performed on a Hg1201 single crystal with an optimized Tc. We have extracted the penetration depth for in-plane currents λ // (0) and the anisotropy ratio γ.