KNIGHT-SHIFT, ELECTRIC-FIELD GRADIENT, AND ELECTRONIC-STATE IN THE SPIN-PEIERLS COMPOUND CUGEO3 - CU-63,CU-65 NMR IN A SINGLE-CRYSTAL

Cu-63,Cu-65 NMR measurements have been performed to study Knight shift and electric-field gradient (EFG) tensors in the spin-Peierls (SP) co mpound CuGeO3, which undergoes the SP transition at T(SP)similar to 14 K, using a single crystal. From the numerical analysis of the Cu-63,C u-65 NMR spectra based on a nuclear Hamiltonian including Zeeman and e lectric quadrupole interactions, we have precisely determined the prin cipal values and axes of the Knight shift and EFG tensors. Based on th eses results, the orbital susceptibility and hyperfine interaction are discussed within a Cu2+ single-ion model in a rhombic crystal field. Consequently, the crystal field parameters are obtained.