INELASTIC-SCATTERING OF LIGHT BY MAGNETIC EXCITONS IN THE PSEUDO ISING ANTI-FERROMAGNETS K2COF4 AND RB2COF4

In addition to previously reported phonon Raman scattering, the authors observed inelastic light scattering by magnetic excitons in K//2CoF//4 and Rb//2CoF//4; the polarized spectra have been studied at low temperatures under an applied magnetic field up to about 5 teslas. The results are interpreted on the basis of a multilevel propagating exciton model deduced from a Hamiltonian including the single ion spin-orbit coupling, the low symmetry crystal field and a nearest neighbors Heisenberg exchange interaction, acting in the **4 GAMMA //4** plus (O//6) ground state of Co**2** plus . The Ising character, which is caused by the low symmetry crystal field, is found to be less marked when evaluated from the magnon dispersion results than it was indicated by previous magnetic measurements, and this was confirmed by recent inelastic neutron scattering data in Rb//2CoF//4.