Anisotropy of the magnetic and transport properties in EuZn$_2$As$_2$

TL;DR

This study compares EuZn₂As₂ and EuCd₂As₂, revealing how differences in magnetic anisotropy and electronic structure influence their magnetic, transport, and Hall effect properties, with implications for Weyl physics.

Contribution

It provides the first detailed comparison of magnetic anisotropy and electronic properties between EuZn₂As₂ and EuCd₂As₂, highlighting the role of spin-orbit coupling and orbital contributions.

Findings

EuZn₂As₂ has a higher Néel temperature (19.6 K) than EuCd₂As₂.

EuZn₂As₂ exhibits reduced magnetic and transport anisotropy.

Electronic structure differences explain variations in Hall effects.

Abstract

Several recent studies have shown that the anisotropy in the magnetic structure of \ECA\ plays a significant role in stabilizing the Weyl nodes. To investigate the relationship between magnetic anisotropy and Weyl physics, we present a comparative study between EuZn$_2$As$_2$ and EuCd$_2$As$_2$ that are isostructural but with different magnetic anisotropy. We performed structural analysis, electronic transport, and magnetization experiments on millimeter-sized single crystals of EuZn$_2$As$_2$, and compared the results to those of EuCd$_2$As$_2$. By combining the first principle calculations and neutron diffraction experiment, we identify the magnetic ground state of EuZn$_2$As$_2$ as A-type antiferromagnetic order with a transition temperature ($T_\mathrm{N}$ = 19.6 K) twice that of EuCd$_2$As$_2$. Like EuCd$_2$As$_2$, the negative magnetoresistance of EuZn$_2$As$_2$ is observed after suppressing the resistivity peak at $T_\mathrm{N}$ with increasing fields. However, the anisotropy in both transport and magnetization are much reduced in EuZn$_2$As$_2$. The difference could be ascribed to the weaker spin-orbit coupling, more localized $d$-orbitals, and a larger contribution from the Eu $s$-orbitals in the zinc compound, as suggested by the electronic band calculations. The same band structure effect could be also responsible for the observation of a smaller non-linear anomalous Hall effect in EuZn$_2$As$_2$ compared to EuCd$_2$As$_2$.