ANALYSIS OF C-13-NMR SPECTRA IN C-60 SUPERCONDUCTORS - HYPERFINE COUPLING-CONSTANTS, ELECTRONIC CORRELATION EFFECT, AND MAGNETIC PENETRATION DEPTH

A C-13-NMR anisotropic hyperfine coupling: tensor was determined as 2 pi(-1.68, -1.68, 3.37) x 10(6) rad/sec for C-60(3-) in A(3)C(60) super conductors, where A is an alkali metal, by analyzing C-13-NMR spectra below 85 K. Combined with an isotropic coupling constant of (2 pi x0.6 9)x10(6) rad/sec, the 2s and 2p characters of the electronic wave func tions at the Fermi level were deduced. The results were compatible wit h local-density-approximation band calculations. From a simulation of C-13-NMR spectra at superconducting state, the traceless chemical (orb ital) shift tensor and isotropic chemical shift were determined as (67 , 34, -101) ppm and similar to 150 ppm, respectively. An estimated mag netic penetration depth is larger than 570 nm in K3C60 Furthermore, th e modified Korringa relation, T(1)TK(2)similar to beta S (with Knight shift K,: spin-lattice relaxation time T-1, and Korringa constant S), clearly showed the existence of weak but substantial antiferromagnetic spin fluctuation in A(3)C(60); beta=0.40-0.58 with an error of +/-20% . The Stoner enhancement factor was also determined as 1-1.5 from a co mparison between spin susceptibility obtained from NMR and band-calcul ation results. [S0163-1829(98)00542-6].