Calculated magneto crystalline anisotropy of decorated and undecorated steps on fcc Co(001)

The in-plane magnetocrystalline anisotropy. of an isolated step along the [ 1 (1) over bar 0] direction. on the surface of fcc Co(0 0 1), is calculated using a multi-orbital tight-binding approach. A similar calculation is per formed on the same system, when the step is 'decorated' with an atomic wire of Cu. Two distinct methods are used, both based on calculations of the to tal energy with the magnetization parallel and perpendicular to the step. O ne method applies the standard recursion scheme with up to 400 levels of co ntinued fraction. in order to achieve the required accuracy of 0.01 meV/ste p atom. The other method is novel, and is based on an exact (semi-analytic) total energy computation of an infinite system using a matrix Mobius trans formation technique. The two methods give essentially identical results and the easy axis of magnetization for the undecorated case is along the step as observed experimentally. Decoration of the step changes the anisotropy i n the same direction as observed by Weber et al. but the shift is insuffici ent to rotate the easy axis. (C) 2001 Elsevier Science B.V. All rights rese rved.