Ni nanowire arrays with different diameters have now been extended to directly fabricate in porous anodic alumina oxide (AAO) templates on Ti/Si substrate by direct current (DC) electrodeposition. An aluminum film is firstly sputter-deposited on a silicon substrate coated with a 300 nm Ti film. AAO/Ti/Si substrate is synthesized by a two-step electrochemical anodization of the aluminum film on the Ti/Si substrate and then used as template to grow Ni nanowire arrays with different diameters. The coercivity and the squareness in parallel direction of Ni nanowires with about 10 nm diameters are 664 Oe and 0.90, respectively. The Ni nanowire arrays fabricated on AAO/Ti/Si substrates should lead to practical applications in ultrahigh-density magnetic storage devices because of the excellent properties. (c) 2006 Elsevier B.V. All rights reserved.