We have observed a magnetic dipole‐active localized mode in MnF2, doped with 0.04 mol% FeF2at 94.8 cm−1at 1.2°K, using an ir lamellar interferometer. To our knowledge, this is the first direct spectroscopic evidence using far ir techniques for a magnetic dipole‐active impurity mode in an otherwise magnetically ordered system. The line has the following features: the half‐width is 0.4 cm−1and the absorption strength ∫&agr;dv∼1 cm−2. With increasing temperature, the line shifts to lower frequencies and finally disappears at about 25°K. Magnetic fields up to 45 kG have been applied parallel to thecaxis of the sample, yielding a linear splitting of the line. Agfactor of 2.3 is derived from the data. The experimental results at 1.2°K can be understood satisfactorily both with a simple molecular field picture and, also, with the help of a simple spin‐wave calculation. In the molecular field approximation, the line is correlated to a transition of the ground spin state to the first excited state of the orbital ground state of Fe2+. The observed value for the frequency is fitted by a Fe2+&sngbnd;Mn2+exchange coupling constantJ=1.9 cm−1in both models. Preliminary results on a localized mode in MnF2:Co2+are also reported.