NMR evidence for coexistence of superconductivity and ferromagnetic component in magnetic superconductor RuSr2YCu2O8: Ru-99,Ru-101 and Cu-63 NMR

From Ru- and Cu-NMR studies, we present evidence for coexistence of superco nductivity and ferromagnetism in a cuprate superconductor RuSr2YCu2O8 (RuY1 212). The observation of a large enhancement of a radio-frequency field for the Ru-NMR signal at zero field reveals the existence of a ferromagnetic ( FM) component in the ordered RuO2 plane below a Curie temperature of T-M = 150 K. Just below the onset temperature of superconductivity T-c(onset) = 4 5 K, a remarkable decrease of the nuclear spin-lattice relaxation rate 1/T- 1 was observed within the ordered RuO2 plane as well as the CuO2 plane, rev ealing that the superconducting gap coexists with the FM component in the R uO2 plane on a microscopic scale. In addition, from the observation of a sh arp peak in (101)(1/T-1) at T-c(zero) similar to 23 K where the resistivity becomes zero, we suggest that the motion of self-induced vortices originat ing from fluctuations of the FM component induces the resistivity between T -c(onset) and T-c(zero) in RuY1212.