Electronic and magnetic properties of single-crystal YNi2B2C from 11B and 89Y NMR and magnetic-susceptibility measurements.

Abstract

The quaternary intermetallic compound superconductor YNi{sub 2}B{sub 2}C with transition temperature {ital T}{sub {ital c}}=15.5 K has been investigated by {sup 11}B and {sup 89}Y nuclear magnetic resonance (NMR) and by magnetic susceptibility {chi} measurements both in the normal and the superconducting states. The NMR and relaxation measurements have been performed in a powder sample and single crystals. {sup 11}B ({ital I}=3/2) NMR spectra display patterns typical for an axially symmetric field gradient with quadrupole coupling frequency {ital v}{sub {ital Q}}=698{plus_minus}1 kHz and {sup 89}Y ({ital I}=1/2) data show spectra typical for a large anisotropic Knight shift, {ital K}, with axial symmetry (3{ital K}{sub ax}=0.042{percent}). In the normal state, the {sup 11}B {ital K} increases with decreasing temperature while {sup 89}Y {ital K} decreases. The temperature dependences of both the isotropic ({ital K}{sub iso}) and anisotropic (3{ital K}{sub ax}) components of the {sup 11}B and {sup 89}Y Knight shifts are presented together with dc magnetic susceptibility ({chi}) measurements obtained from magnetization measurements and are explained by the sharp features of the density of states near the Fermi level in the system. The analysis of the NMR and {chi}({ital T}) data when combined with the theoretical calculation of the Van Vleckmore » contribution to {chi}({ital T}) allows the determination of the hyperfine coupling constants for both nuclei investigated and permits the separation of the different contributions to the total measured {chi}({ital T}). The nuclear spin-lattice relaxation rate (NSLR) ({ital T}{sup {minus}1}{sub 1}) results for {sup 11}B show an enhancement of ({ital T}{sub 1}{ital T}){sup {minus}1} when lowering the temperature, consistent with previous results. (Abstract Truncated)« less