High Concentration Intrinsic Defects in MnSb 2 Te 4 .

MnSb 2 Te 4 has a similar structure to an emerging material, MnBi 2 Te 4 . According to earlier theoretical studies, the formation energy of Mn antisite defects in MnSb 2 Te 4 is negative, suggesting its inherent instability. This is clearly in contrast to the successful synthesis of experimental samples of MnSb 2 Te 4 . Here, the growth environment of MnSb 2 Te 4 and the intrinsic defects are correspondingly investigated. We find that the Mn antisite defect is the most stable defect in the system, and a Mn-rich growth environment favors its formation. The thermodynamic equilibrium concentrations of the Mn antisite defects could be as high as 15% under Mn-poor conditions and 31% under Mn-rich conditions. It is also found that Mn antisite defects prefer a uniform distribution. In addition, the Mn antisite defects can modulate the interlayer magnetic coupling in MnSb 2 Te 4 , leading to a transition from the ideal antiferromagnetic ground state to a ferromagnetic state. The ferromagnetic coupling effect can be further enhanced by controlling the defect concentration.