Crystal-field levels in pure and diluted DyB₂C₂ studied by neutron inelastic scattering technique

Inelastic neutron scattering experiments on Dy¹¹B₂C₂ and Dy_0.07Y_0.93¹¹B₂C₂ have been performed. The results enable us to infer important properties of the crystal-field levels of Dy³⁺ in DyB₂C₂ which has fascinating structural and magnetic properties that are attributed to the electronic states of the Dy ion. While no clear excitation was observed in pure DyB₂C₂, three excitations from the ground state with the energies 1.4, 4.1 and 5.8 meV were observed in Dy_0.07Y_0.93¹¹B₂C₂. By comparing the present results with the previous crystal-field calculation, we infer that the ground state of Dy³⁺ in YB₂C₂ is T₈ which is split into two Kramers doublets by the tetragonal potential. Additionally, the heat capacity measured on the diluted system is compared with a calculation using the low part of the energy level scheme obtained from the neutron experiments. Good agreement between theory and experiment is obtained.