Polar phonons and intrinsic dielectric response of the ferromagnetic insulating spinel CdCr2S4 from first principles -: art. no. 214123

We have studied the dielectric properties of the ferromagnetic spinel CdCr2S4 from first principles. Zone-center phonons and Born effective charges were calculated by frozen-phonon and Berry phase techniques within LSDA+U. We find that all infrared-active phonons are quite stable within the cubic space group. The calculated static dielectric constant agrees well with previous measurements. These results suggest that the recently observed anomalous dielectric behavior in CdCr2S4 is not due to the softening of a polar mode. We suggest further experiments to clarify this point.