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

Choi et al. (Phys. Rev. B 58 (1998) 5166) using low-energy electron diffrac tion 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 effec t and X-ray magnetic circular dichroism experiments it was concluded that t he coupling between Mn and Co in these surface alloys is ferromagnetic in t ype. Using the tight binding linear muffin tin orbitals scheme within an at omic sphere approximation and an local density approximation (LDA) in the f ilm geometry we conclude that Mn in the ordered 1 ML thick Mn0.5Co0.5 surfa ce alloy is in a high spin state of ca. 3.2 mu(B). Both ferromagnetic and a ntiferromagnetic couplings between Mn and Co are obtained but the antiferro magnetic coupling seems to be the preferred type. Going beyond LDA and cons idering a slightly disordered surface alloy should, therefore, be worthwhil e. (C) 2000 Elsevier Science B.V. All rights reserved.