Second-order phase transition in Ca2-xSrxRuO4: A Raman study

We use Raman scattering to study the second-order structural transition in metallic Ca2-xSrxRuO4 for x=0.3. With increasing temperature, the following phonon behaviors are observed in the Raman spectra: the 320cm-1 mode exhibits an enhancement both in peak energy and in intensity near the characteristic temperature TO∼220K; the 374cm-1 mode exhibits a significant decrease in peak energy with increasing temperature toward TO; and the intensity of the 374cm-1 mode gradually decreases with increasing temperature, and finally disappears above 230K. These phonon behaviors suggest that a second-order structural transition occurs in the metallic phase of Ca1.7Sr0.3RuO4 through TO∼220K