Magnetocrystalline Energy, Electronic Charge Distribution, and Fermi Surface of Iron from a Tight-Binding Calculation

Abstract

By introducing the spin-orbit coupling, the first constant ${K}_{1}$ of the magnetocrystalline energy of bcc Fe has been evaluated, using 284 nonequivalent points of the Brillouin zone. Previous results obtained with the tight-binding approximation are used. ${K}_{1}$ is found to be positive, in agreement with the experimental data on the directions of easy magnetization, but its value is lower than expected. The $3d$-electron charge distributions for the ${t}_{2g}$ and ${e}_{g}$ symmetries are given as a function of energy. Both the charge and spin densities show the same kind of deviation from spherical symmetry as the ones deduced, respectively, by x-ray and neutron-diffraction experimental results. Finally, the shape of Fermi surface in paramagnetic and ferromagnetic bcc Fe is suggested.