Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi₂Te₄ Thin Films.

Abstract

Recently, MnBi₂Te₄ has been demonstrated to be an intrinsic magnetic topological insulator and the quantum anomalous Hall (QAH) effect was observed in exfoliated MnBi₂Te₄ flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi₂Te₄ films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a nonsquare hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. We demonstrated that one AH component with the larger coercive field is from the dominant MnBi₂Te₄ phase, whereas the other AH component with the smaller coercive field is from the minor Mn-doped Bi₂Te₃ phase. The extracted AH component of the MnBi₂Te₄ phase shows a clear even-odd layer-dependent behavior. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi₂Te₄ films.