Amorphous magnetism in Fe-B alloys: First-principles spin-polarized electronic-structure calculations

We present self-consistent spin-polarized electronic-structure calculations for amorphous ${\mathrm{Fe}}_{\mathit{x}}$ ${\mathrm{B}}_{100\mathrm{-}\mathit{x}}$ (50≤x≤95) alloys, based on a supercell linear-muffin-tin-orbital technique and realistic structure models produced by molecular-dynamics simulations. We show that the electronic densities of states of the amorphous alloys are very similar to that of the crystalline Fe borides. This confirms the conclusions as to the similarity of the local order in the crystalline and amorphous phases drawn on the basis of the structural studies. The calculated composition dependence of the magnetic moments is in good agreement with experimental data on amorphous films, with a maximum of the magnetic moment close to 15 at. % B. The decrease of the moment for lower B content is shown to arise from the competition between ferro- and antiferromagnetic exchange interactions, the decrease with higher B content is due to a dilution effect: polarizable d-d bonds are replaced by magnetically inert p-d bonds. We also present detailed calculations of the photoemission intensities.