Tuning the magnetic state and topological transition of monolayer Kagome Co3Pb3SSe with large magnetic anisotropy

Abstract

Ferromagnetic topological insulators (TIs) have recently garnered tremendous attention as a platform for investigating novel physical phenomena and innovative design of low-power-consumption spintronic devices. Co₃X₃Y₂ monolayers are a promising topological system with a large quantum anomalous Hall effect (QAHE), but they suffer from low magnetic anisotropy. To address this limitation, we construct a Janus Kagome Co₃Pb₃SSe monolayer by introducing heavy elements to enhance spin–orbit coupling (SOC) and break mirror symmetry. Janus Co₃Pb₃SSe is a Weyl semimetal with a high Chern number (|C| = 3) and a substantial magnetic anisotropy of 2.613 meV per unit. It also exhibits a large band gap of 79.8 meV, which is robust against external strain, and a Curie temperature (T_C) of 167 K. Notably, strain can induce multistate transitions in the material. Under a strain of −1%, attributed to the combined effects of super-exchange and direct exchange, there is a magnetic ground state transition from ferromagnetic (FM) to antiferromagnetic (AFM). At a strain of −2%, a phase transition from a topological insulator (TI) to a metallic state is observed. Under a 5% tensile strain, T_C significantly increases to 348 K, thus enabling the material to be applied at room temperature. Our findings enrich researches on ferromagnetic TIs of Janus Kagome systems.