Negative Magnetoresistance in Antiferromagnetic Topological Insulator EuSn2As2**Supported by the National Key Research and Development Program of China under Grant No. 2016YFA0300402, the National Basic Research Program of China under Grant No. 2015CB921004, the National Natural Science Foundation of China under Grant Nos. 11974095 and 11374261, the Zhejiang Natural Science Foundation (No. LY16A040012), and the Fundamental Research Funds for the Central

Abstract

The measurements of magnetization, longitudinal and Hall resistivities are carried out on the intrinsic antiferromagnetic (AFM) topological insulator EuSn2As2. It is confirmed that our EuSn2As2 crystal is a heavily hole doping A-type AFM metal with the Néel temperature TN = 24 K, with a metamagnetic transition from an AFM to a ferromagnetic (FM) phase occurring at a certain critical magnetic field for the different field orientations. Meanwhile, we also find that the carrier concentration does not change with the evolution of magnetic order, indicating that the weak interaction between the localized magnetic moments from Eu2+ 4f7 orbits and the electronic states near the Fermi level. Although the quantum anomalous Hall effect (AHE) is not observed in our crystals, it is found that a relatively large negative magnetoresistance (−13%) emerges in the AFM phase, and exhibits an exponential dependence upon magnetic field, whose microscopic origin is waiting to be clarified in future research.