EuSn2As2: an exfoliatable magnetic layered Zintl–Klemm phase

Abstract

Despite the immense interest in magnetic, topological, and magnetoelectronic phenomena in isolated layers of 2D materials and their vertically stacked heterostructures, there remains a dearth of 2D magnetic materials that can be readily exfoliated into single layers. Here, we synthesize EuSn₂As₂, the first exfoliatable, layered magnetic Zintl–Klemm phase that features van der Waals bonding between neighboring layers. In these crystals, Eu²⁺ 4f⁷ spins magnetically order at 24 K and are coupled ferromagnetically within each layer and antiferromagnetically, with some potential canting, across adjacent layers. Magnetic ground state DFT calculations and temperature-dependent transport measurements on single crystals together establish that EuSn₂As₂ is semimetallic. Finally, we show that this material can be thinned down to a few layers having steps corresponding to SnAsEuAsSn layers via micromechanical exfoliation. This work opens up further explorations into the design, synthesis, and layer-dependent magnetic properties of exfoliatable, lanthanide-based magnetic van der Waals Zintl phases.