Raman scattering study in iridium pyrochlore oxides

Abstract

Raman scattering spectra of iridium pyrochlore oxides R2Ir2O7 (R=Nd, Sm, and Eu) have been measured. These three compounds undergo metal-insulator transition. Below the transition temperature TMI, new peaks appear for R = Sm and Eu, but no remarkable change for R = Nd. Therefore, Sm2Ir2O7 and Eu2Ir2O7 accompany structural change with the transition, but not the case for Nd. Even if Nd2Ir2O7 deforms, the distortion is different from that of Sm2Ir2O7 and Eu2Ir2O7, because the spectra of Nd are clearly different from those of Sm and Eu below TMI.