Optical Properties of Cobalt

Abstract

The optical reflectance of Co has been measured in the spectral range $0.05 \mathrm{eV}\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}11.8 \mathrm{eV}$. The reflectance is low and decreases monotonically in the region $h\ensuremath{\nu}\ensuremath{\ge}0.05$ eV, indicating that strong absorption has started at photon energies near or below 0.05 eV. The reflectance has small shoulders at about 3.0, 5.0, and 6.0 eV. Optical functions have been deduced from the reflectance data by the Kramers-Kronig analysis. The $\ensuremath{\omega}\ensuremath{\sigma}$ curve exhibits a strong structure at $h\ensuremath{\nu}=6.0$ eV, similar to the strong peak at $h\ensuremath{\nu}=5$ eV of $\ensuremath{\omega}\ensuremath{\sigma}$ of Ni. The absorption coefficient $\ensuremath{\alpha}$ of Co also has a prominent peak at $h\ensuremath{\nu}=6.0$ eV and smaller ones at 3.2 and 5.0 eV. These optical data will be used in a separate paper in conjunction with photoemission results to deduce the optical density of states of Co.