C-13 AND H-1-NMR STUDY OF VORTEX DYNAMICS IN A LAYERED ORGANIC SUPERCONDUCTOR AT SELECTIVE NUCLEAR SITES

The quasi-two-dimensional superconductor, kappa-(BEDT-TTF)(2)Cu(NCS)(2 ), under a perpendicular field was investigated by NMR relaxation rate measurements at the three different nuclear sites. The vortex dynamic s contribution to the relaxation rate was separated from the quasipart icle contribution and found to show a peak formation around 2 K with a site-dependent peak height. The analysis supports that the peak behav ior does not come from the simple crossover but from some qualitative change in the vortex dynamics.