Stability and magnetic properties of Fe double layers on Ir (111)

Abstract

We investigate the interplay between the structural reconstruction and the magnetic properties of Fe doublelayers on Ir (111)-substrate using first-principles calculations based on density functional theory and mapping of the total energies on an atomistic spin model. We show that, if a second Fe monolayer is deposited on Fe/Ir (111), the stacking may change from hexagonal close-packed to bcc (110)-like accompanied by a reduction of symmetry from trigonal to centered rectangular. Although the bcc-like surface has a lower coordination, we find that this is the structural ground state. This reconstruction has a major impact on the magnetic structure. We investigate in detail the changes in the magnetic exchange interaction, the magnetocrystalline anisotropy, and the Dzyaloshinskii Moriya interaction depending on the stacking sequence of the Fe double-layer. Based on our findings, we suggest a new technique to engineer Dzyaloshinskii Moriya interactions in multilayer systems employing symmetry considerations. The resulting anisotropic Dzyaloshinskii-Moriya interactions may stabilize higher-order skyrmions or antiskyrmions.

Topological phases in polar oxide nanostructures

“…In the magnetic case, all mentioned interactions pertain to bulk iron and have been taken from classic references (Kittel, 1966) except the DM coupling, for which we cite the maximum (large) values estimated by electronic-structure calculations of the Fe=Irð111Þ interface (Dupé et al, 2018). In the electric case the dipole-dipole energy is evaluated based on standard polarization and volume data for PbTiO 3 (Bilc et al, 2008) and recalling that ϵ ∞ ≈ 8.6 for this compound (Zhong, King-Smith, and Vanderbilt, 1994); the short-range interaction energy is evaluated taking into account the harmonic interatomic constants reported by Ghosez et al (1999) for nearest neighbor Pb cations; the anisotropy energy is derived from the computed energy difference between the tetragonal and rhombohedral ferroelectric polymorphs of PbTiO 3 ; see King-Smith and Vanderbilt (1994).…”

Unoccupied surface and interface states in Pd thin films deposited on Fe/Ir(111) surface

“…We address initially the two-dimensional Bloch spectral function of fcc-Pd/Fe/Ir(111) surface and discuss the nature of the different unoccupied states showing high intensity at Γ, the center of the two-dimensional Brillouin zone. By investigating the case of bare fcc-Fe/Ir(111) surface, which was shown to host a lattice of skyrmions in its ground state [32][33][34], and considering thicker Pd films deposited on that surface, we aim at distinguishing the states stemming from Pd. Our conclusions are summarized in the last section.…”