Raman study of Ca₃Co₂O₆ single crystals

Abstract

We report Raman scattering experiments on single crystals of Ca₃Co₂O₆. The polarization dependent scattering was used to assign symmetry of the observed vibrational modes. The low temperature experiments show a subtle change in peak widths at 75 K. The increase in the peak widths is also accompanied by a gain in spectral weight for wave numbers greater than 1000 cm^-1. We have associated the increase in peak widths to lattice distortion and the high frequency spectral feature to the inelastic light scattering processes involving two magnons. These observations are consistent with the reported extended x-ray absorption fine structure [Bindu etal, Phys. Rev. B 79, 094103 (2009)] and Mossbauer measurements [Paulose etal, Phys. Rev. B 77, 172403 (2008)] which suggests simultaneous presence of lattice distortion and short range magnetic order in the system well above the Neel temperature (24 K). Thus, our experiments highlight the usage of Raman spectroscopy as a tool to study systems which show precursor effects to magnetic transition.