Magnetic anisotropy of $4f$ atoms on a WSe$_2$ monolayer: a DFT+U study

TL;DR

This study uses DFT+U calculations to explore how different rare-earth atoms on WSe2 monolayers exhibit varied magnetic anisotropies, revealing insights into stable magnetic states for potential single-atom magnets.

Contribution

It provides a comparative analysis of 4f rare-earth atoms on WSe2, highlighting how valence and orbital filling influence magnetic anisotropy and stability.

Findings

RE elements without 5d occupation have larger anisotropy at high densities.

Atoms with outer 5d electrons show larger anisotropy in dilute configurations.

Half-filled 4f shells can produce substantial energy barriers due to hybridization.

Abstract

Inspired by recent advancements in the field of single-atom magnets, particularly those involving rare-earth (RE) elements, we present a theoretical exploration employing DFT+$U$ calculations to investigate the magnetic properties of selected $4f$ atoms, specifically Eu, Gd and Ho, on a monolayer of the transition-metal dichalcogenide WSe$_2$ in the 1H-phase. This study comparatively examines RE with diverse $4f$ orbital fillings and valence chemistry, aiming to understand how different coverage densities atop WSe$_2$ affect the magnetocrystalline anisotropy. We observe that RE elements lacking $5d$ occupation in the atomic limit exhibit larger magnetic anisotropy energies at high densities, while those with outer $5d$ electrons show larger anisotropies in dilute configurations. Additionally, even half-filled $4f$ shell atoms with small orbital magnetic moments can generate substantial energy barriers for magnetization rotation due to prominent orbital hybridizations with WSe$_2$. Open $4f$ shell atoms further enhance anisotropy barriers through spin-orbit coupling effects. This aspect is crucial for the experimental realization of stable magnetic information units.