In giant magnetoresistance (MR) spin valve (SV), the thin nano-oxide layer (NOL) has been used for the confinement of conduction electrons, which contributes to spin scattering in film and its interfaces. In this article, we have investigated the effects of NOLs, which were fabricated by a plasma oxidation of Co-Fe layer on the magnetic properties and MR in a Mn-Ir-Pt-based SV The NOLs were located at the middle of pinned layers and between a free and a metal-capping layer. The adjusted NOL could result in high MR and strong exchange coupling field (H-ex). From a high-resolution electron microscopy analysis, the oxide was formed at about 1 nm. For SVs employing an oxide-capping layer, the strong reflectivity at the interface of a free and an oxide-capping layer should lead to the large decrease of an interlayer coupling field, which could possibly improve H-ex. (C) 2004 Elsevier B.V. All rights reserved.