Effect of adsorbed H atoms on magnetism in monoatomic Fe wires at Ir(100)

By means of ab initio calculations based on density-functional theory we demonstrate that magnetism in monoatomic Fe wires deposited on nanostructured Ir(100) surface can be tuned by their functionalization with hydrogen. The pristine monoatomic Fe wires deposited on nanostructured Ir(100) surface partially covered by H atoms are antiferromagnetic. However, the type of exchange interaction between Fe atoms can be changed by increasing H coverage. At fully hydrogenated Ir surface the Fe wires themselves are decorated with hydrogen, which gives rise to the ferromagnetic coupling between adjacent Fe atoms.

Figure 1

(Color online) Side and top views of (a) quasihexagonal and (b) square Ir(100) surface with periodic monoatomic Ir wires; big gray and small white spheres represent Ir and H atoms, respectively. (c) The surface from Fig. 1b with 0.4 ML of H; (d) total H chemisorption energies $E_{chem}$ as a function of the number of H atoms per $\left(5\times 2\right)$ cell.

Figure 2

(Color online) (a) Fe wires on the ch-Ir(100) surface with H coverage of 0.4 ML; (b) the same surface with H coverage of 1.4 ML; Fe atoms are shown as light blue (dark gray) spheres and H atoms are small white spheres; the arrows indicate magnetic moments of Fe atoms; [(c) and (d)] the simulated STM images of the structures in (a) and (b), respectively. H atoms in (c) and (d) are represented by small black spheres.

Figure 3

(Color online) H adsorption configurations at nanostructured Ir(100) surface decorated with Fe wire. The H coverage is in the range from 0.4 to 1.6 ML [i.e., the number of H atoms per $\left(5\times 2\right)$ cell varies from 4 to 16]. The energies of the structures with the same H coverage are given with respect to the most favorable configuration.

Figure 4

(Color online) (a) Evolution of energy difference between FM and AFM wires with H coverage, calculated for the most favorable H configurations at given coverage; (b) Fe magnetic moments as a function of H coverage.

Figure 5

(Color online) (a) Majority-spin and (b) minority-spin density of states projected on $3d$ orbitals of Fe atoms of pristine ferromagnetic and antiferromagnetic wires [cf. Fig. 2a].

Figure 6

(Color online) Electron density induced upon adsorption of two H atoms in the ${\text{B}}_{\text{Fe-Fe}}$ sites on (a) ferromagnetic and (b) antiferromagnetic Fe wire supported by fully hydrogenated ch-Ir(100) surface. The contour plots are given in the plane determined by Fe atoms and H atoms adsorbed in the ${\text{B}}_{\text{Fe-Fe}}$ sites. The horizontal axis is along direction of the Fe wire and the vertical one is at $67°$ with respect to the Ir(100) terraces.