Raman scattering studies on strontium and ruthenium doped iridium pyrochlore oxides

We report the Raman spectroscopy studies on the strontium and ruthenium doped pyrochlore iridate compound Eu2Ir2O7. Eu2Ir2O7 is Weyl semimetallic oxide which exhibits metal-insulator transition at around 120 K. Strontium doping at the Europium site increases the metallic behavior and the metal-insulator transition temperature also lowers systematically with increasing doping concentrations.Ruthenium doping in the iridium site turns the compound to be completely insulating. The Raman spectroscopy studies show a systematic variation of specific Raman modeswith doping which involves Ir-O-Ir bond bending, Ir-O, and Eu-O bond stretching. Clear variations of peak positions have been observed for T2g(1), A1g and T2g(4) modes. The variations of electron-phonon interactions reflected in the Raman peaks can be attributed to the different electronic ground states of the doped samples. We have also corroborated the Raman peak shifts with the structural parameters obtained from XRD data.