Experimental studies of the magnetic excitations in the 1D Ising-antiferromagnet CsCoCl3

The electronic Raman and infrared absorption spectrum within the ⁴T_1g ground term of the one dimensional antiferromagnet CsCoCl₃ is investigated. At 2K three magnon lines are observed whereas above the magnetic phase transition at 8K the number of lines is increased to twelve. No drastic change of the magnon spectrum is observed in passing the Neél temperature at 21.5K. The magnon spectrum could still be observed at 150K. Theoretically the one-exciton spectrum is described within the molecular field approximation, using an exchange coupling between nearest neighbours along the spin chains only. Satisfactory agreement is obtained between measured and calculated energies.