High aspect ratio cobalt nanowire arrays were fabricated using ac and pulse electrodeposition techniques into the porous alumina templates. The pH was adjusted to be about 4. The effects of electrodeposition time in both the ac and pulse techniques were investigated. Using ac electrodeposition technique, increasing the deposition time significantly decreased the coercivity and squareness. The coercivity and squareness of about 600 Oe and 0.35 were obtained for high aspect ratio Co nanowires, respectively. In the pulse electrodeposition technique, increasing the off-time between the pulses stabilizes the microstructure thereby suppresses the reduction of the coercivity and squareness. A coercivity of about 1400 Oe was seen for high aspect ratio Co nanowires electrodeposited with 200 ms off-time and different pulse numbers. (C) 2008 Elsevier B.V. All rights reserved.