Valence state determines the band magnetocrystalline anisotropy in 2D rare-earth/noble-metal compounds

TL;DR

This study reveals how valence states influence the band magnetocrystalline anisotropy in 2D rare-earth/noble-metal compounds, linking electronic structure to magnetic orientation through experimental and theoretical methods.

Contribution

It demonstrates the impact of valence state and band hybridization on magnetic anisotropy in 2D intermetallic compounds, combining experimental and computational analysis.

Findings

EuAu₂ exhibits out-of-plane easy magnetization due to Eu²⁺ valence.

GdAu₂ shows in-plane magnetization linked to Gd³⁺ and Weyl lines.

Valence state affects magnetic anisotropy across similar compounds.

Abstract

In intermetallic compounds with zero-orbital momentum ($L=0$) the magnetic anisotropy and the electronic band structure are interconnected. Here, we investigate this connection on divalent Eu and trivalent Gd intermetallic compounds. We find by X-ray magnetic circular dichroism an out-of-plane easy magetization axis in 2D atom-thick EuAu$_2$. Angle-resolved photoemission and density-functional theory prove that this is due to strong $f-d$ band hybridization and Eu$^{2+}$ valence. In contrast, the easy in-plane magnetization of the structurally-equivalent GdAu$_2$ is ruled by spin-orbit-split $d$-bands, notably Weyl nodal lines, occupied in the Gd$^{3+}$ state. Regardless of the $L$ value, we predict a similar itinerant electron contribution to the anisotropy of analogous compounds.