Bulk single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3-5 at.% in the near-surface (similar to2000 Angstrom) region. The implantation was performed at similar to350 degreesC to promote dynamic annealing of ion-induced damage. Following annealing at 700 degreesC, temperature-dependent magnetization measurements showed ordering temperatures of similar to300 K for Co- and similar to250 K for Mn-implanted ZnO. Clear hysteresis loops were obtained at these temperatures. The coercive fields were less than or equal to 100 Oe for all measurement temperatures. X-ray diffraction showed no detectable second phases in the Mn-implanted material. One plausible origin for the ferromagnetism in this case is a carrier-induced mechanism. By sharp contrast, the Co-implanted material showed evidence for the presence of Co precipitates with hexagonal symmetry, which is the cause of the room temperature ferromagnetism. Our results are consistent with the stabilization of ferromagnetic states by electron doping in transition metal-doped ZnO predicted by Sato and Katayama-Yoshida [Jpn. J. Appl. Phys. 40 (2001) L334]. This work shows the excellent promise of Mn-doped ZnO for potential room temperature spintronic applications. (C) 2003 Elsevier Ltd. All rights reserved.