Magnetic and crystal-field properties of the magnetic superconductor DyNi₂B₂C from ¹⁶¹Dy Mossbauer spectroscopy

Abstract

We have utilized the ¹⁶¹Dy Mossbauer effect to investigate the magnetic properties and the nature of the ground state of the DyNi₂B₂C quaternary magnetic superconductor (T_N~11 K, T_c~6 K). Detailed analysis of the spectra suggests that the magnetic transition is of first order and the Dy moments of 9.8μ_B at saturation are confined in the basal plane. Isomer shift in this material (~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 B₂⁰ crystal-field parameter is positive and estimated to amount to about 2 K. The ground-state crystal-field doublet is composed primarily of the |±½> 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.