Single-phase Zn0.95Co0.05O and Zn0.90Co0.05Al0.05O samples were prepared by a novel combustion method.Xray diffraction studies exhibit the pure phase wurtzite structure of doped ZnO.Energy dispersive x-ray analysis confirms the incorporation of dopants into the host material.Scanning electron microscopy shows the ordered morphology in both of the samples.Temperature-dependent resistivity analysis describes the expected semiconducting behavior that is similar to the parent ZnO materials.Room-temperature magnetic measurements reveal the absence of ferromagnetism in Co-doped ZnO,while the Co and Al co-doped sample displays apparent room-temperature ferromagnetic behavior.The decrease of resistivity and presence of ferromagnetic behavior in Al-doped ZnCoO system corroborate the significant role of free carriers.Atoms of transition metals (TMs) partially substitute the cation sites of host semiconductor materials to produce diluted magnetic semiconductors (DMSs).Recently,these materials have attracted a great deal of interest due to their potential applications in spin based or spintronic devices.[1-3] The achievement of room-temperature (RT) ferromagnetic behavior in DMSs has been considered to be a very important issue.After the early reports of ferromagnetism in DMSs,[4,5] TM-doped Ⅲ-Ⅴ and Ⅱ-Ⅵ semiconductors have remained under discussion among the scientific community.Among these semiconductor materials,ZnO has been included as one of the best research candidates for the fabrication of DMSs because of its various outstanding properties.Moreover,ZnO has prospective applications in different optical and electronic devices.[6]