Magnetism of amorphous iron: From ferromagnetism to antiferromagnetism and spin-glass behavior

The magnetization of realistic structural models of amorphous iron is calculated self-consistently within the framework of local-spin-density theory. We show that the distribution of the magnetic moments is strongly coupled to fluctuations in the local self-consistent potential. At a density slightly lower than bcc Fe, amorphous iron is predicted to be a strong inhomogeneous ferromagnet. An increase in density leads to a broadening of the bands and a transition to weak magnetism. The transition from strong to weak magnetism is coupled with the appearance of a few negative moments. Further compression induces more spin flips, leading to a substantial antiferromagnetic component in the magnetic polarization. At large compressions, the global magnetovolume effect leads to a reduction of all magnetic moments. The distribution of positive and negative moments overlaps, resulting in a transition to a spin-glass state. Our calculations demonstrate a universal proportionality of the local magnetic moment and the local exchange splitting.