Condensed Matter Physics Seminar
Staging in doped La2CuO4+y and La2-xSrxCuO4+
Department of Physics
University of Connecticut
La2CuO4 can be made superconducting either through substitution of Sr for La or by the addition of excess, interstitial oxygen. Superconducting La2CuO4+d is of interest because the oxygen dopants are mobile and show behavior such as phase separation and layer by layer ordering known as staging. We report our initial results on selected compounds combining magnetization and x-ray diffraction. Slow cooling La2CuO4 in a crucible gives small flat crystals, which we then oxygenated to have a sharp superconducting transition at TC=40K and well-ordered interstitial oxygen at stage 5. Previously, FZ grown crystals oxygenated with the same process also had TC=40K but stage 4 oxygen ordering. Oxidizing crystals with Sr=0.08 raises TC from 16K to 33K. Diffraction studies reveal that any ordering of the CuO6 octahedra are suppressed and may indicate short range ordered staging. Float Zone grown crystals with Sr=0.04 can be oxidized to produce a superconductor with a sharp TC of 40K.
Thursday, March 18, 2004
Gant Science Complex
(The seminar is followed by coffee/tea, cookies, and an informal discussions.)