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Mössbauer measurements have been performed on a GaAs single crystal sample following the implantation of radioactive 57Mn+ (T½ = 1.5 min) ions. The Mn+ ions were implanted with 60 keV energy into a GaAs sample held at temperatures of 300–700 K in an implantation chamber. Implantation fluences were <2 × 1012 ions/cm2 which assured single ion implantations. Mössbauer spectra were measured with a resonance detector equipped with 57Fe enriched stainless steel foils mounted on a conventional drive system outside the implantation chamber. The spectra at the lower temperatures are dominated by an asymmetrically broadened quadrupole split doublet (FeD), assigned to Fe in implantation induced damaged surroundings; at higher temperatures a single line dominates, due to Fe at undisturbed substitutional sites (FeS). The spectra also required small contributions (approx. 13–5%) of a quadrupole split component, FeX, which may be due to interstitial Fe and Fe in vacancy complexes. A prominent annealing stage is evident in the temperature range 300–550 K, leading to substantial increase in the FeS fraction, and attributed to mobile Ga vacancies.