Volume expansion contribution to the magnetism of atomically disordered intermetallic alloys

The origin of magnetism in atomically disordered transition-metal-nonmagnetic (i.e., FeAl) alloys has been investigated by dichroism and diffraction measurements at high pressure and by band structure calculations. The results show that, in contrast to earlier studies, besides the effects of the local environment of the magnetic ions, disorder-induced lattice changes play a key role in the magnetic properties of these systems. We demonstrate experimentally and theoretically that about 35-45% of the magnetic moment of Fe60Al40 alloys arises from lattice expansion effects induced during the disordering process. Such large effects in Fe60Al40 could actually be related to the moment-volume instability observed in these alloys.