Raman Study on the High Temperature Transition in V2O3

We have measured the Raman scatterings of V 2 O 3 and (V 0.985 Cr 0.015 ) 2 O 3 in the temperature range between 300 and 600 K. The Raman frequencies of A 1 g phonon modes in V 2 O 3 show some softening and recovery with a minimum at 480 K in the region of the high temperature transition. Those in (V 0.985 Cr 0.015 ) 2 O 3 decrease monotonically with temperature. The ratio of the scattering intensity of the lowest frequency E g mode to the lower frequency A 1 g mode decreases with temperature in V 2 O 3 . On the other hand, the ratio in (V 0.985 Cr 0.015 ) 2 O 3 is relatively independent of temperature. These experimental results are discussed in light of the two-bands crossing model proposed by Zeiger for the high temperature transition in V 2 O 3 . The Raman lines due to A 1 g phonon mode show an anomalous asymmetric line shape, which is interpreted by the Fano resonance effect between the A 1 g phonon and the electronic transitions in an a 1 g -bonding band.