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 magnetic properties and the nature of the ground state of the DyNi2B2C quaternary magnetic superconductor (T-N similar to 11 K, T-c similar to 6 K). Detailed analysis of the spectra suggests that the magnetic transition is of first order and the Dy moments of 9.8 mu(B) at saturation are 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 which implies charge transfer from 6s orbitals of Dy onto the strongly bonded C atoms. The second-order B-2(0) crystal-field parameter is positive and estimated to amount to about 2 K. The ground-state crystal-field doublet is composed primarily of the \+/-1/2] component of the J=15/2 free ion term. Higher-order crystal-field terms should be included in the exchange crystal-field Hamiltonian for a detailed account of the experimental results.