Granular alloys of iron with other transition metals have been fabricated in both Al2O3and SiO2matrices. Both stable (Fe‐Ni, Fe‐Co) and metastable (Fe‐Cu) alloys have been achieved. Under appropriate deposition conditions, the grains are single‐phase alloys ranging in size from 15 to 50 A˚. Superparamagnetism and enhanced coercivity have been observed, and the effect of grain size on these phenomena has been investigated. We have also studied the effects of the different insulating matrices.