Amorphous magnetism in iron-boron systems: First-principles real-space tight-binding LMTO study

We have performed ab initio spin-polarized self-consistent calculations of the electronic structure and magnetic moments in the series of the ${\mathrm{Fe}}_{100\mathrm{-}\mathit{x}}$ ${\mathrm{B}}_{\mathit{x}}$ glasses (0<x<60) with the real-space tight-binding LMTO method. Realistic atomic models consisting of 500 to 864 atoms in a cubic box with periodic boundary conditions were constructed with the use of the Monte Carlo method. The systems studied show itinerant magnetism with the net magnetic moment on iron sites, μ¯, saturating at the maximum value in a region of a (hypothetical) amorphous iron. The iron magnetic moment decreases upon dilution with boron atoms with no maximum on the compositional dependence of μ¯. The calculated distribution of the iron moments is narrow with the width decreasing towards the boron-rich end of the series. The magnetovolume effect is shown to be noticeable in iron-rich glasses, declining with increasing boron content. No evidence of a tendency to form the spin-glass state has been found in iron-rich borides.