Magnetic ground state of supported monatomic Fe chains from first principles

TL;DR

This paper introduces a new computational method combining conjugate gradient and Newton-Raphson techniques within spin-density functional theory to determine the magnetic ground states of supported monatomic Fe chains, validated against experiments and models.

Contribution

A novel ab initio optimization scheme for accurately identifying magnetic ground states of atomic chains on substrates.

Findings

Fe chains on Rh(111) have magnetic ground states consistent with Heisenberg model predictions.

Spin-spiral configurations are observed for Fe chains on Nb(110), indicating higher order interactions.

Wavelengths of spin-spirals on Re(0001) match experimental STM data.

Abstract

A new computational scheme is presented based on a combination of the conjugate gradient and the Newton-Raphson method to self-consistently minimize the energy within spin-density functional theory, thus to identify the ground state magnetic order of a cluster of magnetic atoms. The applicability of the new \textit{ab initio} optimization method is demonstrated on Fe chains deposited on different metallic substrates. The obtained magnetic ground states of the Fe chains on Rh(111) are analyzed in details and a good comparison is found with those gained from an extended Heisenberg model containing first principles based interaction parameters. Moreover, the effect of the different bilinear spin-spin interactions in the formation of the magnetic ground states is monitored. In case of Fe chains on Nb(110) spin-spiral configurations with opposite rotational sense are found as compared to previous spin-model results which hints on the importance of higher order chiral interactions. The wavelength of the spin-spiral states of Fe chains on Re(0001) was obtained in good agreement with scanning tunneling microscopy experiments.