Low-frequency spin dynamics as probed by 63Cu and 199Hg NMR in HgBa2CuO4+δ superconductors with different oxygen content

Cu-63 and Hg-199 nuclear magnetic resonance was performed on a series of powder HgBa2CuO4+delta samples with different oxygen content delta in order to study the influence of oxygen doping on the spin dynamics in the normal and superconducting state. The spin-lattice relaxation time T-1 of Hg-199 and Cu-63 nuclei were measured over a wide range of temperature at different orientations of the crystallites with respect to the magnetic field. For the optimally doped sample (T-c=96 K) we compared our experimental results to numerical calculations of the spin-lattice relaxation rate as a function of temperature below T-c for several types of the order parameter symmetry: isotropic s wave, anisotropic s wave without nodes, s wave with nodes, and d wave, using the different values of the gap parameter 2 Delta/k(B)T(c) within the AF fluctuation model. The comparison with our experimental relaxation data shows that for Hg-199 nuclei in the orientation B(0)parallel to(a,b) plane as well as for Cu-63 nuclei in both orientations, B(0)parallel to(a,b) plane and B(0)parallel to c axis, the experimental results are in coincidence with the d(x2-y2)-wave symmetry with the gap parameter 2 Delta/k(B)T(c)=7.02. [S0163-1829(99)09801-X].