Anisotropy of the magnetic and transport properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">EuZn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Zhicheng Wang, Emily Been, Jonathan Gaudet, Gadeer Alqasseri, Kyle Fruhling, Xiaohan Yao, U. Stuhr, Qinqing Zhu, Zhi Ren, Yi Cui, Chunjing Jia, Brian Moritz, Sugata Chowdhury, Thomas Devereaux, Fazel Tafti
Abstract
Several recent studies have shown that the anisotropy in the magnetic structure of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ 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 ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$ and ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ that are isostructural but with different magnetic anisotropy. We performed structural analysis, electronic transport, and magnetization experiments on millimeter-sized single crystals of ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$, and compared the results to those of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$. By combining the first principle calculations and neutron diffraction experiment, we identify the magnetic ground state of ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$ as A-type antiferromagnetic order with a transition temperature (${T}_{\mathrm{N}}$ = 19.6 K) twice that of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$. Like ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$, the negative magnetoresistance of ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$ 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 ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$. 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 nonlinear anomalous Hall effect in ${\mathrm{EuZn}}_{2}{\mathrm{As}}_{2}$ compared to ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$.