Local-spin-density-functional theory is applied to describe the structural and magnetic properties of iron wires consisting of chains of single atoms. It is shown that an unsupported isolated wire is unstable with respect to both dimerization and bending. The preferential positions of wires grown on stepped $\mathrm{Cu}\mathrm{}\left(11n\right)\mathrm{}$ surfaces are the inner corner sites of the steps. From the total energy differences the effective intrachain and interchain exchange constants are estimated for wires at different distances. In all cases the resulting magnetic order is ferromagnetic. Regarding an array of magnetic moments arranged in parallel rows as a quasi-two-dimensional $\mathrm{XY}$ ferromagnet subject to uniaxial anisotropy with the easy axis parallel to the surface, we find the Curie temperature of Fe wires on Cu(117) using Monte Carlo simulation. Our results are consistent with a critical behavior characteristic of the $\mathrm{XY}$ model.

• Received 13 December 2001

DOI:https://doi.org/10.1103/PhysRevB.65.235405