The role of structural variations in the magnetism of Fe/Cu(1 1 1): First-principles calculations

Abstract

The effects of three crucial structural variations, i.e., sub-monolayer coverage, intermixing, and stacking fault, on the magnetism of Fe/Cu(1 1 1) were quantitatively investigated using density functional theory calculations. A single Fe atom (0.25 ML) on the fcc (2 × 2) Cu(1 1 1) surface has a higher magnetic moment (3.18 μ B) than bulk Fe (2.15 μ B). The calculated magnetic moments of 0.5, 0.75 and 1 ML coverage Fe on the Cu(1 1 1) surface, were 3.01 μ B, 2.87 μ B and 2.72 μ B, respectively. For intermixing between 1 ML of Fe and Cu(1 1 1), the magnetic moment of the Fe adatoms monotonically decreased with the intermixing amount. The electron density of states showed that the decreasing magnetic moment of Fe adatoms resulted from the filling of down-spin 3 d-electrons below Fermi level by the hybridization of 3 d-electron among Fe atoms. The influence of Cu(1 1 1) atoms on the electronic structure and magnetic moment was observed to be negligible. In the artificially prepared 2 and 3 ML thick Fe films on Cu(1 1 1), the magnetic moments of Fe atoms were not dependent on the stacking sequences of Fe layers. However, the demagnetization energy calculation revealed a more stable perpendicular magnetization for fcc Fe films compared to hcp Fe films on Cu(1 1 1). In brief, the structure dependence of magnetism of Fe films on Cu(1 1 1) mainly originates from the bonding among Fe atoms, while the effect of bonding with Cu atoms was negligible.