Effect of Fe on Bi2Te3: Structure, magnetic properties, and XPS valence band

The crystal structure and magnetic properties of Fe doped Bi2Te3 are presented. The samples were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetization measurements. Rietveld refinement results show a decrease in volume due to the decrease in c lattice parameter as iron is introduced. By XPS measurements, the Te 3d, Bi 4f, Bi 5d, Te 4d, and Fe 3d core levels were identified, and the XPS valence band (VB) was measured. The deconvolution process of high resolution XPS spectra in Fe 3d orbital shows that the Fe3+ ion is present in the samples. Theoretical calculations by DFT reveal that the Bi2Te3 compound is a semiconductor with a narrow energy band gap in agreement with experimental results. DOS analysis shows that the main contributions to the valence band are the Te 5p, Bi 6p, and Fe 3d states. XPS VB shows a decrease in the intensity at zero eV due to increased Fe 3d states and good correspondence with DOS calculated for Bi2Te3. Finally, magnetic susceptibility measurements on Bi2Te3 do not show a magnetic behavior; however, for the doped sample with x = 0.2, a weak ferromagnetic behavior (WFM) below 14 K is observed.