MgO single crystals were implanted with 70 keV C/N/O ions at room temperature with respective doses of 2 x 10(16) and 2 x 10(17) ions/cm(2). All samples with high-dose implantation showed room temperature hysteresis in magnetization loops. Magnetization and slow positron annihilation measurements confirmed that room temperature ferromagnetism in O-implanted samples was attributed to the presence of Mg vacancies. Furthermore, the introduction of C or N played more effective role in ferromagnetic performance than Mg vacancies. Moreover, the magnetic moment possibly occurred from the localized wave function of unpaired electrons and the exchange interaction formed a long-range magnetic order. (C) 2012 Elsevier B. V. All rights reserved.