Influence of Mn Concentration on Magnetic Topological Insulator Mn_xBi_2-xTe₃ Thin-Film Hall-Effect Sensor

Hall-effect (HE) sensors based on high-quality Mn-doped Bi₂Te₃ topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi₂Te₃. The sensors with low Mn concentrations, Mn_xBi_2-xTe₃, x =0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x=0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that of the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.