Raman scattering in doped transition metal pentatellurides

We have measured the Raman spectra of Sb doped (ZrTe5−xSbx; 0<x<0.25) and Hf doped (ZryHf1−yTe5; 0<y<1) pentatellurides in the 90–300 cm−1 range, and compared them to the corresponding spectrum for the parent material ZrTe5. X-ray diffraction data revealed that the pentatelluride structure prevails at all doping concentrations. With increasing Sb concentration, the linewidths for three of the four Raman peaks observed at 115, 120, and 147 cm−1 in the parent material broadened with insignificant change in the linewidth for the fourth peak at 180 cm−1. Interestingly, the peak intensity for the mode at 180 cm−1 gradually diminishes in ZrTe5−xSbx up to x=0.15, and completely vanishes in the x=0.20 compound. On the other hand, the electrical and Raman properties of ZryHf1−yTe5 exhibit a systematic shift from the corresponding properties of ZrTe5 to that of HfTe5 for increasing Hf concentration in the sample. Implications of the disappearance of the resistivity anomaly with concomitant vanishing of 180 cm−1 Ram...