Hyperfine-field contributions ofs-type orbitals in iron

Theoretical spin densities and hyperfine-field contributions of s-type orbitals in iron are presented. The results for iron metal are obtained from relativistic band-structure calculations where exchange and correlation are accounted for by the local potential of von Barth and Hedin. The dependence of the hyperfine results on the underlying approximation for exchange and correlation is studied for the neutral iron atom and for a number of positive ions. In addition, we compare relativistic versus nonrelativistic calculations. For iron metal we obtain a Fermi-contact field of -37.3 T which is to be compared with the observed total magnetic hyperfine field of -33.8 T. The calculated spin densities for ${\mathrm{Fe}}^{3+}$ agree well with the respective experimental ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ data. The theoretical Fermi contact field for ${\mathrm{Fe}}^{3+}$ comes out 20 T lower than the observed ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ total magnetic hyperfine field.