Ion implantation of Mn at concentrations of 1–5 at. % was performed in AlxGa1-xP:C (x=0, 0.24, 0.38, and 0.54) epilayers grown by gas source molecular beam epitaxy. Ferromagnetic-like ordering at 300 K was observed for Mn doses up to 3 at. % for all Al subfractions in superconducting quantum interference device measurements. The calculated magnetic moment was found to peak at 3 at. % Mn in plots of magnetization versus Mn for all four Al subfractions. For a given Mn concentration, the magnetic moment was found to initially increase then decrease in plots of magnetization versus Al subfraction. Structural characterization revealed the presence of the Mn2P and Mn3Ga phases in Al0.54Ga0.46P:C layers implanted with 5 at. % Mn, while no second phases were observed in any other combinations of Al and Mn. A substantial increase in magnetic ordering temperature predicted by theory for AlxGa1-xP:C films compared to GaP:C films with Mn incorporation was not observed. © 2003 American Vacuum Society.