Structural, electronic, and magnetic properties of a Ni monolayer on Ag(001): Ni adsorption versus Ag surface segregation

The structural, electronic, and magnetic properties of a p(1×1) Ni overlayer on Ag(001) are investigated with use of the highly precise all-electron total-energy full-potential linear augmented-plane-wave (FLAPW) method. Although the Ni-Ag bond length remains essentially the same as that of p(1×1) Ni/Cu(001), we found that the Ni magnetic moment (0.57B) is enhanced by 50% from that (0.39B) of Ni/Cu(001) as a result of the effect of negative pressure. Nevertheless, the magnetic moment is reduced by about 20% compared with that (0.70B) of the surface layer in Ni(001) due to hybridization coupling of Ni and Ag. The magnetic hyperfine field is found to be reduced at the interface due to the direct contribution from conduction electrons. Self-consistent charge and spin densities, work function, single-particle energy bands, and layer-projected density of states for Ni/Ag(001) are also presented. The negligible exchange splitting observed in the photoemission experiment of Thompson et al. is explained in terms of possible Ni subsurface layer formation (Ag segregation to the surface) which is found, from separate self-consistent calculations, to have a lower total energy and a very small (nearly dead) magnetic moment (0.02B).