Magnetically stabilized Mn–Co surface alloys on Co(001)

Choi et al. (Phys. Rev. B 58 (1998) 5166) using low-energy electron diffraction recently displayed an ordered Mn–Co alloy at the surface of Co for a 0.3–0.8 equivalent monolayer of Mn on Co(001). From magneto optic Kerr effect and X-ray magnetic circular dichroism experiments it was concluded that the coupling between Mn and Co in these surface alloys is ferromagnetic in type. Using the tight binding linear muffin tin orbitals scheme within an atomic sphere approximation and an local density approximation (LDA) in the film geometry we conclude that Mn in the ordered 1 ML thick Mn0.5Co0.5 surface alloy is in a high spin state of ca. 3.2 μB. Both ferromagnetic and antiferromagnetic couplings between Mn and Co are obtained but the antiferromagnetic coupling seems to be the preferred type. Going beyond LDA and considering a slightly disordered surface alloy should, therefore, be worthwhile.