Magnetic-field dependence of planar copper and oxygen spin-lattice relaxation rates in the superconducting state of YBa2Cu3O7

The authors report nuclear spin-lattice relaxation rates, W1, for planar copper and oxygen sites in the superconducting state of YBa2Cu3O7. These measurements were made with the static magnetic field along the c axis at a variety of static magnetic-field strengths. The data show that the relaxation rate of 17O depends on magnetic-field strength at low temperature and confirm a similar result for 63Cu. The importance of these measurements is that they give the zero-field limit necessary for comparison with theory. The weak-field data at low temperature for both copper and oxygen have a temperature dependence close to T3, which is the result expected for spin-singlet, orbital d-wave pairing and does not seem compatible with orbital s-wave pairing