First-principles study of hyperfine fields in a Cd impurity in the Fe/Ag(100) interface - art. no. 144419

Monolayer-resolved hyperfine fields (HFF's) at the Fe/Ag(100) interface hav e recently been determined using In-111 probe atoms, which decay to Cd-111, in perturbed gamma gamma angular-correlation spectroscopy (PAC). Isolated radioactive probe atoms in PAC allow to sense the presence of HFF's at the Fe and induced HFF's at the Ag layers but, poses a complementary physical p roblem to that of the HFF's at the host Fe/Ag system: that of an impurity w ithin the layers. Using density-functional theory (DFT) within the generali zed gradient approximation (GGA) and a supercell approach, we investigate t his problem. Similarly as experimentalists insert the probe atom on a layer -by-layer growth, preparing samples with radioactive probe atoms either in the Fe/Ag interface, or in the second (from the interface) Ag layer, or emb edded within the bulk Fe, Our supercell methodology can simulate each of th ese systems. The theoretical approach has the advantage of having the capab ility of distinguishing between two different cases at the interface: Cd in the Fe or Ag side. This allows us to make a clear assignment of the measur ed HFF's. We discuss: (i) the relation of the HFF in the Cd probe with that of the original host atom, (ii) the precision of state of the art DFT-GGA calculations to obtain quantitative predictions of HFF's in very complex sy stems such as interfaces and the effect of lattice relaxations (interlayer spacings, lateral displacements). The importance of including spin-orbit co upling and the influence of additionally considering orbital polarization a re assessed.