The perturbed angular correlation method was used to study intrinsic defects in polycrystalline material, following the implantation of radioactive 111In or 111mCd ions. Measurements were performed at temperatures ranging from 300 to 1450K, under various O partial pressures. Well-defined electric field gradients were observed at temperatures below 900K, near to the Co/CoO phase boundary. During annealing at temperatures above 1100K, an effect of the O activity upon the perturbed angular correlation spectra was detected. This permitted identification of the defect complexes. Unlike the case of 111In probe implantation, no trapping of defects occurred after implantation of isovalent 111mCd probes. This demonstrated the importance of the probe charge state when studying ionic compounds.

T.Wenzel, M.Uhrmacher, K.P.Lieb: Philosophical Magazine A, 1995, 72[4], 1099-120