Electron‐paramagnetic‐resonance linewidths at theM=+1/2↔−1/2 transition of the Fe3+spectrum of Fe/MgO single crystals have been examined at 9 GHz and 300 K before and after ion bombardment. The nominal ion concentrations ranged from 310 to 4300 ppm. Specimens were bombarded at 150 keV with argon ions for up to 12 min. The ion‐bombardment produces reductions in the peak‐to‐peak linewidth of &Dgr;Hpp, which occurred in two stages for all the specimens examined. ©1995 American Institute of Physics.