Tuning of magnetic and transport properties in Bi2Te3 by divalent Fe doping

We report the doping effect of a magnetic Fe ion in Bi2Te3, that is, Bi2-xFexTe3 (x = 0, 0.08, 0.15, 0.2, 0.25, and 0.3). The paramagnetic magnetization data reveal that the Fe ions are doped in the divalent form. The Fe2+ state substituted for Bi3+ can create hole donors, which compensate for the electron dopants of Bi2Te3 with a small amount of Te excess. This causes the n-type carrier density to be decreased with increasing x, and finally be changed to p type at x = 0.3, where the carrier mobility suddenly drops and the electrical resistivity abruptly increases. These results are consistent with angle-resolved photoemission spectroscopy experiments. The Fermi level shifts downward with increasing x. Furthermore, we find a larger spin polarization for the Fe-doped Bi2Te3 samples, which is crucial for future spintronics applications.