Isotope Effect, Magnetic and Transport Properties of High T sub c Superconductors

Physical properties of copper oxide based superconductors and related compounds have been studied with particular emphasis on electrical transport and magnetic properties of single crystals and polycrystalline samples. In La sub (2-x) Sr sub (x) CuO sub 4 we found in addition to the well-known Neel point, T sub N, a magnetic anomaly at T~120K. In the Sr concentration range where T sub N rapidly varies with x, the 120K anomaly is independent of x. In an attempt to study the contribution of the linear Cu- O chains in Ba sub 2 YCu sub 3 O sub 7, we interrupted these chains by partially removing oxygen at relatively low temperatures (Zr gettering).