Raman spectra of CrO2 and MoO2 single Crystals

The Raman spectra of single crystals of CrO₂ and MoO₂ have been studied from 77°K to 500°K for a comparison with the heavily damped phonon features in metallic VO₂. The spectrum of MoO₂ is very similar to that of monoclinic VO₂ whereas CrO₂ exhibits phonon spectra similar to rutile with no appreciable change at the ferromagnetic c curie temperature. The results are discussed with respect to the various models proposed for the semiconductor-to-metal transition in VO₂.