High-field optical spectroscopy of the chromium spinel CdCr₂O₄

We have performed high-field optical spectroscopy measurements of the geometrically frustrated chromium spinel oxide CdCr₂O₄ in the visible light region. We succeeded in observing the pure exciton excitation peak, and identified some other absorption peaks as exciton-magnon excitation peaks from the theoretical calculations of density of states of the spin wave. Furthermore, from the high-field experiment, large variations of absorption peaks were observed at around 4 T. This result indicates that some magnetic phase transition occurs around this field