The topological insulators Bi_2-xFe_xSe_3–xS_x have been investigated by the dc-magnetization, magneto-transport and angle resolved photoemission spectroscopy (ARPES) techniques. With doping of Fe and S, a negative giant magneto-resistance (MR) is observed for parallel electric and magnetic fields (H||E). The MR behavior at lower magnetic field can be explained with the semi-classical theory whereas the MR behavior at higher field has been attributed to the axial anomaly. Interestingly, the system reached to the quantum limit at low magnetic field (∼ 4.5T). The magnetic ordering can be explained with the presence of both the RKKY (surface) and van-Vleck (bulk) interaction. The ARPES study reveals that a surface gap is suppressed when the magnetic ordering changes from ferromagnetic to anti-ferromagnetic ordering. The ARPES study and the appearance of quantum oscillations (SdH) in the resistivity pattern reveal that the topological surface property is preserved with the co-doping of Fe and S.

拓扑绝缘体 Bi _2-x Fe _x Se _3–x S _x已通过直流磁化、磁输运和角分辨光电子能谱 (ARPES) 技术进行了研究。随着 Fe 和 S 的掺杂，对于平行电场和磁场 ( H||E ) 观察到负巨磁电阻 (MR)）。低磁场下的 MR 行为可以用半经典理论来解释，而高磁场下的 MR 行为则归因于轴向异常。有趣的是，该系统在低磁场（~4.5T）下达到了量子极限。磁性排序可以用 RKKY（表面）和 van-Vleck（体）相互作用来解释。ARPES 研究表明，当磁性排序从铁磁性变为反铁磁性排序时，表面间隙会受到抑制。ARPES 研究和电阻率模式中量子振荡 (SdH) 的出现表明，Fe 和 S 的共掺杂保留了拓扑表面特性。