Anomalous temperature dependence of Cu NMR line width and magnetization in YBa2Cu3O7-δ

We report an anomalous temperature dependence of the magnetization and the NMR line width at the planar Cu(2) and oxygen sites in the mixed state of aligned YBa2Cu3O7-δ powder at relatively high field (≥ 30 kOe), where hysteresis of the magnetization due to flux pinning is not important. Both the magnetization and the NMR line width at all sites show a steep increase at low temperature. We found a much larger line width at Cu(2) sites than at oxygen sites when the magnetic field is applied perpendicular to the c-axis, indicating a very microscopic local field modulation. © 1989