NMR analysis of the electronic structure of superconducting yttrium carbide halides

摘要

Nuclear magnetic resonance and relaxation are reported for C-13, Br-79/81 and I-127 in the layered carbide halides Y2C2Br2, Y2C2Br0.5I1.5, Y2C2I2 and Y2CBr2 for natural isotope abundances and for C-13-enriched samples, Field and temperature dependences of C-13 spin-lattice relaxation are derived. The data analysis supports p-like character of the conduction electrons at the C-2 dumbbell sites in the superconducting dicarbides. Nonlinear temperature dependence of the C-13 Korringa rate in Y2C2Br2 indicates that the Fermi energy falls in a region of positive curvature of the energy-dependent density of states. (C) 1998 Elsevier Science S.A. [References: 11]