Spin-Optical-Phonon Interaction in Antiferromagnetic CoF2

Spin-optical-phonon interaction is observed in Co${\mathrm{F}}_2$ by the transfer of magnetic dipole intensity to the otherwise optically inactive $E_g$ phonons. Theory predicts that the temperature dependence of the intensity is caused by the change in longitudinal spin correlation, and the change in energy and thermal population of the magnetic excitations. Experimentally, only the latter are important in Co${\mathrm{F}}_2$.