Revealing magnetism in the distorted kagome $R$Ti$_3$Bi$_4$ ($R$ = Nd, Sm, Gd) via ARPES and XMCD

TL;DR

This study combines ARPES, DFT, and XMCD techniques to explore the electronic and magnetic properties of $R$Ti$_3$Bi$_4$ kagome metals, revealing surface states, magnetic moments, and their relation to quantum phenomena.

Contribution

It provides new insights into the electronic structure and magnetism of $R$Ti$_3$Bi$_4$ kagome materials, highlighting the role of surface states and magnetic moments.

Findings

Bulk electronic bands are dominated by Ti hybridization.

Surface state identified at the $Gamma$ point.

GdTi$_3$Bi$_4$ exhibits a small magnetic moment driven by Gd proximity.

Abstract

Kagome materials are known for hosting emergent quantum phenomena driven by the interaction between different lattice, charge and spin orders. Here, we present a detailed angle resolved photoemission (ARPES), density functional theory (DFT) and x-ray magnetic circular dichroism (XMCD) study of the electronic and magnetic structure of $R$Ti$_3$Bi$_4$ ($R$ = Nd, Sm, Gd). ARPES and DFT demonstrate that the bulk electronic band structure is dominated by the hybridization of the Ti bands, and the weak electron-like pocket at $\Gamma$ is identified as a surface state. The isotropic XAS profile of the $M_{4,5}$-edge of the rare earth is consistent with the presence of $R^{3+}$ oxidation state. Using the XMCD sum rules, backed by the atomic multiplet theory calculations, we obtain the spin and orbital magnetic moments. The Ti $L_{2,3}$-edge XMCD reveals the presence of a small magnetic moment in GdTi$_3$Bi$_4$, presumably driven by the proximity of the {Ti} kagome layers to the $zigzag$ chains of Gd, while the total magnetic moment of Gd is shared by the $f$ and $d$ electrons. Our combined XMCD, ARPES and DFT study brings an important piece of information to understand the spin flip transitions and anomalous Hall effect observed in the $R$Ti$_3$Bi$_4$ kagome metals.