Low-energy interband absorption in bcc Fe and hcp Co

Abstract

We have examined the electronic structure of bcc Fe and single-crystal hcp Co by using optical absorptivity and thermoreflectance techniques for $0.2\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}5$ eV. The optical conductivities $\ensuremath{\sigma}$ were calculated by Kramers-Kronig analyses. A prominent structure was observed in $\ensuremath{\sigma}$ for Fe at 2.37 eV and a shoulder was observed near 0.8 eV; the latter structure was the dominant feature in the thermoreflectance spectrum. These were discussed in terms of minority-spin band interband absorption and spin-flip interband transitions. The anisotropic optical conductivities of hcp Co were discussed in terms of recent energy-band calculations.