MAGNETIC AND CRYSTAL-FIELD PROPERTIES OF THE MAGNETIC SUPERCONDUCTOR DYNI2B2C FROM DY-161 MOSSBAUER-SPECTROSCOPY

We have utilized the Dy-161 Mossbauer effect to investigate the magnet ic properties and the nature of the ground state of the DyNi2B2C quate rnary magnetic superconductor (T-N similar to 11 K, T-c similar to 6 K ). Detailed analysis of the spectra suggests that the magnetic transit ion is of first order and the Dy moments of 9.8 mu(B) at saturation ar e confined in the basal plane. Isomer shift in this material (similar to 0.5 mm/s) is significantly less than that observed in metallic Dy w hich implies charge transfer from 6s orbitals of Dy onto the strongly bonded C atoms. The second-order B-2(0) crystal-field parameter is pos itive and estimated to amount to about 2 K. The ground-state crystal-f ield doublet is composed primarily of the \+/-1/2] component of the J= 15/2 free ion term. Higher-order crystal-field terms should be include d in the exchange crystal-field Hamiltonian for a detailed account of the experimental results.