Photoemission Investigation of the Electronic Structure of Dysprosium

Abstract

Photoemission measurements in the spectral range from the threshold $\phi$ at 3.2 eV to 11.8 eV have been obtained from evaporated films of dysprosium. The energy distribution of the emitted electrons and the quantum yield were measured at room temperature and below the magnetic-ordering temperatures. The optical transitions are predominantly nondirect and temperature-independent. A high density of $d$-like states is observed near the Fermi energy ($E_F$), with a peak at $E-E_F=-0.3\mathrm{}\pm 0.1$ eV and a shoulder at $E-E_F=1.1\mathrm{}\pm 0.1$ eV. The width of the $s$- and $d$-like filled states is 5.5±0.2 eV. These observations are in very good agreement with recent band calculations. No structure is observed in the empty states for $E-E_F>4\mathrm{}$ eV. The emission of inelastically scattered electrons is observed in the energy distributions and their contribution to the measured distribution is estimated with a simple model. The scattering is attributed to contamination of the sample by residual gases in the vacuum. As a result of the scattering effects, only an estimate of the optical density of filled states is obtained for $E-E_F<-2.0\mathrm{}$ eV. As a sample ages, an additional peak appears in the energy distributions at $E-h\nu +\phi =2.7\mathrm{}\pm 0.1$ eV, and it is attributed to emissions from states produced by sample contamination. Structure in the energy distributions is also observed at $E-h\nu +\phi =6.3\mathrm{}\pm 0.2$ eV. The possibility that the latter structure is due to $f$ states is discussed. The data obtained at temperatures below the magnetic-ordering temperatures show no measurable effect. Thus, shifts due to magnetic ordering in the filled density of states are less than 0.3 eV. As expected, the general properties of the optical density of states for dysprosium are very similar to those obtained for gadolinium.