Controlled incorporation of Mn into Sb₂Te₃ using molecular beam epitaxy to grow highly ordered crystals

Intrinsic magnetic topological materials in the MB₂T₄-family (M= V or Mn, B= Bi or Sb, T= Te) were predicted to show intrinsic axion insulator behavior and quantum anomalous Hall (QAH) effect. Incorporation of M in the B₂T₃ crystal structure changes it from a quintuple layer (QL) structure to septuple layers (SL) of the form T-B-T-M-T-B-T. Even though each SL is ferromagnetic, they couple antiferromagnetically when stacked into the bulk, making it difficult to reach zero field QAH conductance. In addition, studies have shown that separating SLs with QLs turns the resulting structure into a ferromagnet (FM). Here we report the growth by molecular beam epitaxy of Mn doped Sb₂Te₃ where the incorporation of Mn in the lattice can be accurately controlled. High crystalline quality materials with varying effective Mn atomic % from 1% to 32%, where pure MnSb₂Te₄ corresponds to 14%, are achieved by adjusting the Mn to Sb flux ratios during growth, while keeping other variables constant. FM behavior with high T_c values was obtained for all the samples with more than 6% Mn, as witnessed by large anomalous Hall signal with coercive field ~0.1 T at 2 K. Relationship between the structural properties and the magnetic behavior will be discussed.