  We investigate theoretically the ground state of the FeMn binary alloy
monolayer on the W(001) surface, the stability of different magnetic
configurations (ferro/antiferromagnetic, disordered local moments, etc.) and
estimate concentrations at which a transition occurs between different magnetic
orders. The tight-binding linear muffin-tin orbital method combined with the
coherent potential approximation is used to treat the surface alloy
appropriately. We discuss the role of disorder on the phase transitions in
surface alloys composed from two different 3d transition metals.

Materials Science