Magnetic properties of finite Co chains on Pt(111)

We present first-principles calculations of the magnetic moments and magnetic anisotropy energies of finite monoatomic Co-n (1less than or equal tonless than or equal to10) chains deposited along the (110) direction on top of a fcc Pt(111) surface. The calculations were performed fully relativistically using the embedded-cluster technique within the Korringa-Kohn-Rostoker method. The magnetic anisotropy energy was evaluated by means of the magnetic force theorem. As a direct consequence of the reduced coordination number of the Co atoms, we found enhanced spin and orbital moments as well as enhanced anisotropy energies in the Co chains as compared to a Co overlayer on Pt(111). For the Pt atoms adjacent to the Co atoms, however, we obtained induced magnetic moments smaller than in the case of a Co monolayer on Pt(111). The moments and the contributions of the individual atoms to the magnetic anisotropy energy depend characteristically on the position within the chains, i.e., on the local environment of the individual atoms. Independent of the length of the chains we found that the easy axis is perpendicular to the surface. The size of the calculated magnetic anisotropy energy and of the anisotropy of the orbital moment fits very well to available experimental values for monoatomic Co chains deposited on a Pt(997) surface.