We present a systematic study of the influence of various types of structural imperfections on the magnetic properties of ultrathin transition-metal films on noble-metal substrates. As a case study, we show by means of ab initio electronic structure calculations that recently predicted ferromagnetism of perfect Ru and Rh monolayers on a Ag(001) substrate is highly sensitive to noninteger coverage by additional Ru or Rh atoms and overlayer-substrate interdiffusion. Both types of structural imperfections strongly reduce the local magnetic moments and lead, in some cases, to a complete extinction of the ferromagnetic state.

• Received 7 September 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2551