Moessbauer studies on novel high-T sub(c) (Sn,Sr)-doped La sub(2-2x)Sr sub(2x)Cu sub(1-x)Sn sub(x)O sub(4) superconductors

摘要

For La sub(2-2x)Sr sub(2x)Cu sub(1-x)Sn sub(x)O sub(4) (x identical with 0.075, 0.090 and 0.110) superconductors, the effects of Sn-doping on local microstructure is studied by means of Moessbauer spectroscopy. The results show that Sn ions in the 4+ valence state dominantly occupy Cu sites rather than La(Sr) site. In the view of the effective oxygen content (or excess oxygen), the dual role of Sn dopant on the carrier concentration is discussed. We attempt to explain the high transition temperature T sub(c) in (Sr, Sn)-doped La sub(2-2x)Sr sub(2x)Cu sub(1-x)Sn sub(x)O sub(4) samples under the model of amphoteric effect of Sn-doping on the concentration.