Magnetic phase transitions in the 1D ising antiferromagnet CsCoCl3

We report on Raman scattering from the magnons in CsCoCl₃ with particular emphasis on two magnetic phase transitions occurring at T_N = 20.82 K and at 8 K. The T → 0 magnon spectrum is fitted by a $\text{S =}\text{1}\text{2}$ anisotropic Heisenberg model. With a simple cluster model we can explain the temperature behaviour of the magnon frequencies and intensities. The physics of the 8 K phase transition is also discussed.