Raman spectra of a misfit layered Ca3 Co4 O9 single crystal

Abstract

The polarized Raman spectra have been measured on misfit layered Ca3 Co4 O9 single crystal, with the temperature range of 9-300 K. Nine phonon modes have been found in parallel polarization configurations and six in cross polarization configurations. The frequencies of the phonon modes related to the vibration of oxygen atoms show anomalous temperature dependence below the metal-insulator transition temperature 50 K (Tc). It is discussed in terms of spin-phonon coupling and the reorganization of the electronic states below Tc. © 2007 The American Physical Society.