Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd$_2$As$_2$

TL;DR

This study investigates the magnetic order and charge transport in EuCd$_2$As$_2$, revealing a magnetic structure that influences its Dirac semimetal properties and causes significant magnetoresistive effects.

Contribution

It provides the first detailed analysis of magnetic order evolution in EuCd$_2$As$_2$ and links magnetic structure to electronic properties in this Dirac semimetal candidate.

Findings

EuCd$_2$As$_2$ exhibits A-type antiferromagnetic order below 9.5 K.

Magnetoresistive effects are strongly affected by magnetic field-induced changes.

Dirac dispersion is present but gapped below the magnetic ordering temperature.

Abstract

We use resonant elastic x-ray scattering to determine the evolution of magnetic order in EuCd$_2$As$_2$ below $T_\textrm{N}=9.5$\,K, as a function of temperature and applied magnetic field. We find an A-type antiferromagneticstructure with in-plane magnetic moments, and observe dramatic magnetoresistive effects associated with field-induced changes in the magnetic structure and domain populations. Our \textit{ab initio} electronic structure calculations indicate that the Dirac dispersion found in the nonmagnetic Dirac semimetal Cd$_3$As$_2$ is also present in EuCd$_2$As$_2$, but is gapped for $T < T_\textrm{N}$ due to the breaking of $C_3$ symmetry by the magnetic structure.