Relationship between disorder, magnetism and band topology in Mn(Sb_1–xBi_x)₂Te₄ single crystals

We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_1−xBi_x)₂Te₄ single crystals grown by large-temperature-gradient chemical vapor transport method. It is found that the ferromagnetic MnSb₂Te₄ changes to antiferromagnetism with Bi doping when x ≥ 0.25. Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_Sb/Bi and Mn site Mn_Mn have a strong influence on the magnetic ground states of these systems. With the decrease of Mn_Mn and increase of Mn_Sb/Bi, the system will favor the ferromagnetic ground state. In addition, the rapid decrease of T_C/N with increasing Bi content when x ≤ 0.25 and the insensitivity of T_N to x when x > 0.25 suggest that the main magnetic interaction may change from the Ruderman–Kittel–Kasuya–Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.