Crystal structure and magnetic properties in semiconducting Eu_3-δZn _xSn _yAs₃with Eu-Eu dimers

Magnetic structure and crystal symmetry, which primarily determine the time-reversal and inversion symmetry, may give rise to numerous exotic quantum phenomena in magnetic semiconductors and semimetals when arranged in different patterns. In this work, a new layered magnetic semiconductor, Eu3-δZnxSnyAs3, was discovered and high-quality single crystals were grown using the Sn flux. According to structural characterization by x-ray diffraction and atomic-resolution scanning transmission electron microscopy, Eu3-δZnxSnyAs3 is found to crystallize in a hexagonal symmetry with the space group P63/mmc (No. 194). After examining different specimens, we conclude that their stoichiometry is fixed at ∼Eu2.6Zn0.65Sn0.85As3, which meets the chemical charge balance. Eu3-δZnxSnyAs3 is composed of septuple (Eu1-δSnyAs2)-Eu-(ZnxAs)-Eu sequences. The shortest Eu-Eu distance in the system is between two Eu layers separated by ZnxAs along the c-axis. Magnetization measurement shows an antiferromagnetic ordering in Eu3-δZnxSnyAs3 at TN ∼12 K, where the magnetic easy-axis is along the c-axis, and Mössbauer spectroscopy observes magnetic hyperfine splitting on Eu and Sn at 6 K. Magnetic anisotropy is significantly different from the ones along the ab-plane in other layered Eu-based magnetic semimetals. Heat capacity measurements confirm the magnetic transition around 12 K. Electrical resistivity measurement indicates semiconductor behavior with a band gap of ∼0.86 eV. Various Eu-based magnetic semiconductors could provide a tunable platform to study potential topological and magnetic properties.