RAMAN AND INFRARED STUDIES OF THE ONE-DIMENSIONAL ANTIFERROMAGNET CSNICL3

Group-theory-predicted Raman-active and infrared-active phonons of CsNiCl3 are detected at various temperatures. Their frequency, damping, and oscillator strength appear to be sensitive to the magnetic ordering over the temperature range studied. Calculated short-range-interaction force constants uncover the dominant role played by the Cl-Cl and Ni-Cl bonds in defining the magnetic properties of the system. Moreover, the observation at low temperature of sharp structures in the Raman spectrum leads us to surmise that they correspond to quantization of the magnetic excitation continuum.