Cu NMR spectra and relaxation in rutheno-cuprate RuSr2GdCu2O8

Abstract 63,65 Cu NMR spectra and relaxation measurements in RuSr2GdCu2O8, in the temperature range 5– 300 K , are reported. From the second-order quadrupole broadening of the NMR line the quadrupole coupling constant turns out ν Q ≃28.5 MHz . NMR line broadening, possibly related to Ru spins ordering, is observed on cooling. The spin-lattice relaxation rates 2W, involving the in-plane magnetic correlation length, do not show critical behavior above the ordering temperature. On approaching the superconducting transition 2W displays a temperature dependence similar to the one in underdoped YBCO.