This paper describes a simple and effective approach to fabrication of aligned magnetic ferrite nanofibers by magnetic-field-assisted electrospinning coupled with oxygen plasma treatment. Large and flexible magnetic hybrid membranes of aligned Fe(3)O(4)/PVP composite nanofibers were fabricated readily by electrospinning mixtures of Fe(3)O(4)/PVP in a magnetic field. The PVP matrix could be removed either by calcination or by oxygen plasma treatment. Oxygen plasma treatment retained the original crystalline phase of Fe(3)O(4), and large inorganic membranes of aligned ferrite nanofibers were obtained: The ferrite nanofibers showed ferromagnetic behaviors, and are promising in flexible magnetic membranes, magnetic separation, drug delivery, and magnetic sensors. (C) 2009 Elsevier Ltd. All rights reserved.