Temperature dependence of the localized magnon mode in MnF2 : Co

The localized magnon mode in MnF₂ : Co was studied by far infrared resonance techniques. The halfwidth at 8 K is 1 cm^-1, about three times smaller than that obtained by other experimental methods. Therefore, accurate measurements of the temperature dependence are possible between 8 and 40 K. The temperature dependence of the effective g-factor is attributed to spin wave renormalization. The half width is magnetic field dependent at higher temperatures and can be approximated by a T² law.