Magnetic anisotropy and chirality of frustrated Cr nanostructures on Au(111)

TL;DR

This study uses relativistic first-principles calculations to explore magnetic anisotropy and chirality in Cr nanostructures on Au(111), revealing complex magnetic ground states and chiral degeneracy lifting.

Contribution

It provides detailed insights into the magnetic anisotropy, Dzyaloshinskii-Moriya interactions, and chirality effects in Cr nanostructures on Au(111), including unconventional magnetic states.

Findings

Frustrated 120° Néel ground state in Cr trimers.

Chiral degeneracy lifted by up to 15 meV in mono-layers.

Different DM interactions observed for various stackings.

Abstract

By using a fully relativistic embedded cluster Green's function technique we investigated the magnetic anisotropy properties of four different compact Cr trimers (equilateral triangles) and Cr mono-layers deposited on Au(111) surface in both fcc and hcp stackings. For all trimers the magnetic ground state was found a frustrated 120$^\circ$ N\'eel configuration. Applying global spin rotations to the magnetic ground state, the predictions of an appropriate second order spin Hamiltonian were reproduced with high accuracy by the first principles calculations. For the Cr trimers with adjacent Au atoms in similar geometry we obtained similar values for the in-plane and out-of-plane anisotropy parameters, however, the Dzyaloshinskii-Moriya (DM) interactions appeared to differ remarkably. For two kinds of trimers we found an unconventional magnetic ground state showing 90$^\circ$ in-the-plane rotation with respect to the high symmetry directions. Due to higher symmetry, the in-plane anisotropy term was missing for the mono-layers and distinctly different DM interactions were obtained for the different stackings. The chiral degeneracy of the N\'eel configurations was lifted by less then 2 meV for the trimers, while this value raised up to about 15 meV per 3 Cr atoms for the hcp packed mono-layer.