Raman spectroscopic study of structural transformation in ordered double perovskites La2CoMnO6 bulk and epitaxial film

• Structural transition in bulk/films of La2CoMnO6 is shown using Raman spectroscopy.
• Raman spectra showed softening of phonons below structural transition temperature.
• Epitaxial films of La2CoMnO6 is grown on SrTiO3 single crystal substrate.
• The width of the Raman modes showed anomaly around structural transition temperature.

Raman spectra of polycrystalline bulk compound and epitaxial thin films of La2CoMnO6 grown on (001) oriented SrTiO3 substrates have been measured between 300 K and 823 K. The polarization dependence of the spectra collected on films provides clear evidence for ordered P21/n structure at room temperature. The high temperature spectra showed appearance of two new modes and simultaneous disappearance of couple of modes above 523 K for bulk and above 583 K in films which is close to previously reported P21/n to R-3 structural transition temperature. The structural transition is seen to accompany softening and anomalous changes in peak widths of stretching and anti-stretching modes indicating significant changes in the tilts in oxygen octahedra around the cations.