Signatures of crossover between weak anti-localization to weak localization effect in Gd doped Sb2Te3 single crystal

The single crystalline growth and characterization of Gd doped Sb2Te3 topological insulator is discussed in this article. The single crystals of Sb2Te3 and Gd0.25Sb1.75Te3 are synthesized by solid-state reaction route via self-flux method. The crystalline nature and structural details of the as grown crystals are investigated through X-ray diffraction (XRD) on both finely crushed powder and mechanically cleaved flake. The appearance of (00 l) diffraction planes in XRD confirmed the single crystal nature of both pure and Gd doped Sb2Te3. The Scanning electron microscopic images and Energy dispersive X-ray analysis confirmed the layered growth of single crystal and near stoichiometric composition of both crystals, respectively. Vibrational modes of both crystals are studied by Raman spectroscopy, showing the occurrence of distinct A11g, E2g and A21g modes. Both, pure and Gd doped crystals exhibited metallic behavior down to 2 K. For pure sample, the high field (up to 14Tesla) transport showed huge + ve MR (up to 547%) at 2 K, whereas in low field (< 1Tesla) a v-type cusp is also observed. Interestingly for Gd doped sample, not only the + ve MR value is decreased (180%, 14 Tesla, 2 K), the same is nearly negligible at 100 K. The magneto-transport results are further discussed in terms of Hikami-Larkin-Nagaoka equation and a systematic crossover between weak anti-localization to weak localization with the Gd doping in bulk topological insulator (Sb2Te3) is envisaged.