Magnetic and electronic structure of the layered rare-earth pnictide EuCd$_2$Sb$_2$

TL;DR

This study investigates the magnetic structure of EuCd$_2$Sb$_2$, revealing an antiferromagnetic order below 7.4 K, and shows how magnetic fields influence its electronic properties, including the formation of a gapped Dirac point.

Contribution

The paper combines resonant elastic X-ray scattering, magneto-transport measurements, and ab initio calculations to elucidate the magnetic and electronic structure of EuCd$_2$Sb$_2$, highlighting the coupling between Eu spins and Dirac electrons.

Findings

EuCd$_2$Sb$_2$ exhibits antiferromagnetic order below 7.4 K.

Magnetic field induces changes in the magnetic structure affecting magnetoresistance.

Electronic structure calculations predict a gapped Dirac point near the Fermi level.

Abstract

Resonant elastic X-ray scattering (REXS) at the Eu $M_5$ edge reveals an antiferromagnetic structure in layered EuCd$_2$Sb$_2$ at temperatures below $T_\textrm{N}$ = 7.4 K with a magnetic propagation vector of $(0,0,1/2)$ and spins in the basal plane. Magneto-transport and REXS measurements with an in-plane magnetic field show that features in the magnetoresistance are correlated with changes in the magnetic structure induced by the field. Ab initio electronic structure calculations predict that the observed spin structure gives rise to a gapped Dirac point close to the Fermi level with a gap of $\Delta E \sim$0.01 eV. The results of this study indicate that the Eu spins are coupled to conduction electron states near the Dirac point.