Crystal fields in ${\mathrm{Er}}_{0.02}$${\mathrm{Y}}_{0.98}$ studied by neutron scattering

The splitting of the $J=\frac{15}{2}$ multiplet of Er in an hcp crystal field has been determined by inelastic neutron scattering from a single crystal of ${\mathrm{Er}}_{0.02}$${\mathrm{Y}}_{0.98}$. Least-squares fits to the spectra gave crystal-field parameters $B_{20}=-0.34\mathrm{}\pm 0.04$, $B_{40}=(0.7\mathrm{}\pm 0.2)\times {10}^{-3\mathrm{}}$, $B_{60}=(0.21\mathrm{}\pm 0.02)\times {10}^{-4\mathrm{}}$, and $B_{66}=(-0.30\mathrm{}\pm 0.03)\times {10}^{-3\mathrm{}}$ in K, in good agreement with results from bulk magnetization data. A significant line broadening of 1.0 meV full width at half-maximum was clearly observed in the first excited state at 2.2 meV.