Band structure and Fermi surface of hcp ferromagnetic cobalt

Abstract

A Korringa-Kohn-Rostoker first-principles computation of the band structure of ferromagnetic hcp cobalt is reported. A muffin-tin potential and a Kohn-Sham exhange-correlation potential were used in conjunction with a rigid exchange splitting. Twelve energy bands in $\frac{1}{24\mathrm{th}}$ of the hcp Brillouin zone were calculated as well as the density of states and the Fermi surface. The exchange splitting was found to be 1.39 eV and a total density of states at the Fermi level of 15.61 electrons/(atom Ry). The spin-orbit coupling constant ${\ensuremath{\xi}}_{3d}$ has been computed and is equal to 6 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}3}$ Ry. The essential features of the band structure agreed with the requirements of the itinerant-electron model of ferromagnetism of the Stoner-Wohlfarth theory. Our resulting density of states was able to explain the available photoemission data. The calculated Fermi surface is in good agreement with the de Haas-van Alphen experiments, particularly for the neck of the point $\ensuremath{\Gamma}$ in the spin-up Fermi surface. The spin-orbit interaction has been taken into account in a qualitative way in order to explain the orbits around $L$ in the spin-down Fermi surface. A comparison with the existing experimental data has permitted us to estimate the mass enhancement due to many-body effects at the $\ensuremath{\Gamma}$ neck as 1.04, resulting in a value of 0.81 for the electron-magnon contribution.