Antisite-Defects Control of Magnetic Properties in MnSb₂Te₄

The intrinsic magnetic topological materials Mn(Sb/Bi)₂Te₃ have attracted extensive attention due to their topological quantum properties. Although, the Mn-Sb/Bi antisite defects have been frequently reported to exert significant influences on both magnetism and band topology, their formation mechanism and the methods to manipulate their distribution and concentration remain elusive. Here, we present MnSb₂Te₄ as a typical example and demonstrate that Mn-Sb antisite defects and magnetism can be tuned by controlling the crystal growth conditions. The cooling rate is identified as the primary key parameter. Magnetization and chemical analysis demonstrate that a slower cooling rate would lead to a higher Mn concentration, a higher magnetic transition temperature, and a higher saturation moment. Further analysis indicates that the Mn content at the original Mn site (Mn_Mn, 3a site) varies more significantly with the cooling rate than the Mn content at the Sb site (Mn_Sb, 6c site). Based on experimental observations, magnetic phase diagrams regarding Mn_Mn and Mn_Sb concentrations are constructed. With the assistance of first-principles calculations, it is demonstrated that the Mn-Sb mixing states primarily result from the mixing entropy and the growth kinetics. The present findings offer valuable insights into defects engineering for preparation of two-dimensional quantum materials.