We report the doping effect of a magnetic Fe ion in Bi${}_2$Te${}_3$, that is, Bi${}_{2-x}$Fe${}_x$Te${}_3$ ($x$ $=$ 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 Fe${}^{2+}$ state substituted for Bi${}^{3+}$ can create hole donors, which compensate for the electron dopants of Bi${}_2$Te${}_3$ 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 Bi${}_2$Te${}_3$ samples, which is crucial for future spintronics applications.

• Received 28 January 2013

DOI:https://doi.org/10.1103/PhysRevB.87.201105