Magnetism of surface alloys of the type MxN1−x/Rh(1 1 1)

We present a density functional theory study on the magnetic properties of two-dimensional surface alloys of the type M_xN_1−x (M=Fe, Co and Ni; N=Pt, Au, Ag, Cd and Pb) on Rh(1 1 1) for x=0.0, 0.25, 0.33, 0.5, 0.67, 0.75 and 1.0, in two types of geometric arrangements—striped phases or linear-chain type, and non-striped phases or mixed checkerboard type. Many pairs among these are bulk-immiscible but show mixing on the surface. We find that the trend in the magnetic moment of surface alloys of N with a given M follows the number of valence electrons in N: the higher the number of valence electrons, the lower the magnetic moment. Overlayer atoms when put on hcp sites show higher moment compared to fcc sites. In general, for a given composition x, linear-chain type structures show a reduced magnetic moment compared to checkerboard type structures. We find that Pb, when alloyed with magnetic elements (Fe, Co and Ni), has a lowering effect on their magnetic moments.