Eu-based Zintl-phase materials EuA2Pn2 (A = Mg, In, Cd, Zn; Pn = Bi, Sb, As, P) have generated significant recent interest owing to the complex interplay of magnetism and band topology. Here, we investigated the electronic, magnetic, and electronic properties of the layered Zintl-phase single crystals of EuMg2Sb2 with the trigonal CaAl2Si2 crystal structure (space group P3ˉm1). Electrical resistivity measurements complemented with angle-resolved photoemission spectroscopy (ARPES) studies find an activated behavior with the intrinsic conductivity at high temperatures indicating a semiconducting electronic ground state with a narrow energy gap of 370 meV. Magnetic susceptibility and zero-field heat-capacity measurements indicate that the compound undergoes antiferromagnetic (AFM) ordering at the Neel temperature TN = 8.0(2) K. Zero-field neutron-diffraction measurements reveal that the AFM ordering is A-type where the Eu ordered moments (Eu2+, S= 7/2) arranged in ab-plane layers are aligned ferromagnetically in the ab plane with the Eu moments in adjacent layers aligned antiferromagnetically. We also find that Eu-moment reorientation in the trigonal AFM domains within the ab planes occurs below TN at low fields < 0.05 T due to very small in-plane anisotropy. Although isostructural semimetallic EuMg2Bi2 is reported to host Dirac surface states, the observation of narrow-gap semiconducting behavior in EuMg2Sb2 implies a strong role of spin-orbit coupling in tuning the electronic states of these materials.
@article{arxiv.2204.05261,
title = {A-type antiferromagnetic order in semiconducting EuMg$_2$Sb$_2$ single crystals},
author = {Santanu Pakhira and Farhan Islam and Evan O'Leary and M. A. Tanatar and Thomas Heitmann and R. Prozorov and Adam Kaminski and David Vaknin and D. C. Johnston},
journal= {arXiv preprint arXiv:2204.05261},
year = {2022}
}