POSSIBLE 4D FERROMAGNETISM OF RH AND RU OVERLAYERS ON A AG(001) SUBSTRATE

The possibility of 4d ferromagnetism is explored for Rh and Ru overlayers on a Ag(001) substrate using the full-potential linearized augmented-plane-wave method. The overlayer relaxation is found to be very small and to have no significant effect on the electronic and magnetic properties. The ferromagnetism of Rh/Ag(001) can be destroyed by an additional Ag layer-which attributes the lack of ferromagnetism in recent surface magneto-optic Kerr-effect experiments to the surface segregation between Rh and Ag atoms. However, Ru/Ag(001) is predicted to be ferromagnetic with both a larger magnetic moment and larger magnetic energy even after being covered by a Ag layer, and thus is more suitable for experimental verification. For both the Rh and Ru cases, the total hyperfine field is predicted to be too small for detecting these possible magnetism. Finally, the considerably strong overlayer-substrate Coulomb repulsion effect indicates that Ag is no longer the "benign" substrate for 4d overlayer magnetism that it is for the 3d metals.