Complex magnetism of the two-dimensional antiferromagnetic Ge2F: from a Néel spin-texture to a potential antiferromagnetic skyrmion

Abstract

Based on density functional theory combined with low-energy models, we explore the magnetic properties of a hybrid atomic-thick two-dimensional (2D) material made of germanene doped with fluorine atoms in a half-fluorinated configuration (Ge₂F). The Fluorine atoms are highly electronegative, which induces magnetism and breaks inversion symmetry, triggering thereby a finite and strong Dzyaloshinskii–Moriya interaction (DMI). The magnetic exchange interactions are of antiferromagnetic nature among the first, second and third neighbors, which leads to magnetic frustration. The Néel state is found to be the most stable state, with magnetic moments lying in the surface plane. This results from the out-of-plane component of the DMI vector, which seems to induce an effective in-plane magnetic anisotropy. Upon application of a magnetic field, spin-spirals and antiferromagnetic skyrmions can be stabilized. We conjecture that this can be realized via magnetic exchange fields induced by a magnetic substrate. To complete our characterization, we computed the spin-wave excitations and the resulting spectra, which could be probed via electron energy loss spectroscopy, magneto-Raman spectroscopy or scanning tunneling spectroscopy.