Ferromagnetism is observed below $10\mathrm{K}$ in $\left[{\mathrm{Bi}}_{0.75}{\mathrm{Te}}_{0.125}{\mathrm{Mn}}_{0.125}\right]\mathrm{Te}$. This material has the BiTe structure, which is made from the stacking of two Te-Bi-Te-Bi-Te blocks and one Bi-Bi block per unit cell. Crystal structure analysis shows that Mn is localized in the ${\mathrm{Bi}}_2$ blocks, and is accompanied by an equal amount of ${\mathrm{Te}}_{\mathrm{Bi}}$ antisite occupancy in the ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ blocks. These ${\mathrm{Te}}_{\mathrm{Bi}}$ antisite defects greatly enhance the Mn solubility. This is demonstrated by comparison of the $\left[{\mathrm{Bi}}_{1-x}{\mathrm{Mn}}_x\right]\mathrm{Te}$ and $\left[{\mathrm{Bi}}_{1-2x}{\mathrm{Te}}_x{\mathrm{Mn}}_x\right]\mathrm{Te}$ series; in the former, the solubility is limited to $x=0.067$, while the latter has $x_{\max }=0.125$. The magnetism in $\left[{\mathrm{Bi}}_{1-x}{\mathrm{Mn}}_x\right]\mathrm{Te}$ changes little with $x$, while that for $\left[{\mathrm{Bi}}_{1-2x}{\mathrm{Te}}_x{\mathrm{Mn}}_x\right]\mathrm{Te}$ shows a clear variation, leading to ferromagnetism for $x>0.067$. Magnetic hysteresis and the anomalous Hall effect are observed for the ferromagnetic samples.

• Received 11 April 2006

DOI:https://doi.org/10.1103/PhysRevB.74.184429