Zero-field magnetic ground state of EuMg${}_2$Bi${}_2$

Abstract

Layered trigonal EuMg${}_2$Bi${}_2$ is reported to be a topological semimetal that hosts multiple Dirac points that may be gapped or split by the onset of magnetic order. Here, we report zero-field single-crystal neutron-diffraction and bulk magnetic susceptibility measurements versus temperature $\chi (T)$ of EuMg${}_2$Bi${}_2$ that show the intraplane ordering is ferromagnetic (Eu${}^{2+},S=7/2$) with the moments aligned in the $ab$-plane while adjacent layers are aligned antiferromagnetically (i.e., A-type antiferromagnetism) below the Néel temperature.