Mu-Sr Studies Of Oxide-Superconductors

The negative muon spin rotation method (mu-SR) has been applied to studies of electronic states at oxygen sites of oxide superconductors YBa2Cu3O7, Nd(2-x)Ce(x)CuO4-delta (x = 0.15, oxygen reduced), LiTi2O4 and related oxide-insulators La2CuO4-delta, CuO, Cu2O. The paramagnetic shifts of mu- trapped at oxygen nuclei in these polycrystalline powder samples have been measured at 300 K. All the measured shifts are positive. In copper-oxides the paramagnetic shifts are of the order 10(-3), while in LiTi2O4 is very small (8.4 +/- 3.34 x 10(-5)). In YBa2Cu3O7, a fast mu- spin relaxation time T2* (approximately 200 ns) has been observed; the reason for this is unknown and further studies are now in progress.