Electronic and magnetic structure of 4f atomic chains on Au(111) substrate*

The study of low-dimensional magnetic systems has been greatly enhanced by the unique ability to create one- (1D) and two-dimensional atomic arrangements of magnetic atoms on a variety of substrates.  These studies have focused on transition metal atoms and islands deposited on insulating and metallic surfaces, including superconductors.  Scanning probe techniques have unveiled rich magnetic phase diagrams and different excitation spectra.  We direct here our attention to the study of 1D atomic chains formed by rare-earth 4f systems on the Au(111) surface, and study their electronic and magnetic configurations by different theoretical techniques.  Ab initio calculations using VASP with GGA+U and HSE functional, with and without spin-orbit interactions, allow for full structural relaxation of the system. 1D chains of Eu atoms on Au(111) surface show minimal charge transfer, reflecting physisorption of neutral Eu on gold.  Different spatial and magnetic configurations and relative spin orientations are parameterized in terms of a spin-Hamiltonian with collinear and non-collinear exchange interactions, as spin-orbit coupling on the substrate is substantial.  Typical exchange parameters of ~0.5 meV promise readily observable characteristics in low-temperature experiments.  Luttinger-Tisza and exact diagonalization approaches of the spin system predict interesting phase diagrams for these structures.