Lattice vibration modes in CdCr2O4

In geometric frustration magnets, spin-lattice coupling can play an important role in lifting the magnetic frustration. In order to understand the mechanism, we have performed inelastic synchrotron x-ray measurements on a single crystal of a frustrated magnet CdCr2O4 that undergoes such a three-dimensional spin-Peierls phase transition at T{\_}N = 7.8 K. Our data taken above and below T{\_}N could be well explained by the rigid ion model, which led to a full identification of the lattice vibration modes in CdCr2O4. A phonon anomaly that might be associated with the transition, however, was not observed.