Nanostructured arrays in two and three dimensions are known to exhibit novel properties. Magnetic nanobowl arrays of cobalt (Co) and cobalt ferrite (CoFe2O4) have been fabricated by vacuum assisted infiltration of precursors inside the interstitial spaces of a colloidal template of polystyrene (PS) latex spheres (1 mu m diameter). Template removal was carried out by annealing followed by toluene etching, which leaves an array of cobalt or cobalt ferrite nanobowls. The coercivity of cobalt nanobowls was found to be greater than the coercivity of cobalt nanoparticles of the same size range; the coercivity of cobalt ferrite nanobowls was greater than that of cobalt nanobowls. (c) 2005 Elsevier B.V. All rights reserved.