A Y-89 NMR-STUDY OF YBA2CU4O8

High resolution Y-89 NMR shift and relaxation time measurements on YBa2Cu4O8 have been performed between 80 and 380K. The shift at room temperature, approximately -50ppm, is somewhat smaller than for fully oxygenated YBa2Cu3O7-delta and the relaxation time is longer. Below approximately 200K the shift starts to decrease rapidly, behaving very like YBa2Cu3O6.8. A comparison of the shift with the Cu-63 perpendicular-to (2) data shows that they have the same temperature dependence, indicating a common susceptibility, and that the ratio of the Cu-63 perpendicular-to (2) to Y-89 hyperfine coupling constants is the same as for YBa2Cu3O7-delta. The temperature dependence of the relaxation behaviour is not Korringa like but is similar to that of YBa2Cu3O6.8.