The Structures of Co90Fe10/Cu multilayers were investigated by X-ray anomalous scattering techniques. it is found that the Cu/Co90Fe10 and Co90Fe10/Cu interfaces have different thermal behavior upon annealing. For the as-deposited sample, a Cu2Co intermixing region exists at the Cu/Co90Fe10 interface, while the Co90Fe10/Cu interface is sharp. There exists only a Co70Fe30 sublayer close to the interface in the Co90Fe10 layer. After annealing at 285 degrees C for 2 h, more Cu react with Co to create a Cu3Co intermixing region at the Cu/Co90Fe10 interface, while no obvious change is observed at the Co90Fe10/Cu interface. The X-ray diffuse scattering measurements performed with the incident X-ray energy close to Fe, Co and Cu K edges, respectively, revealed an island growth mechanism of the rnultilayers. (c) 2005 Elsevier B.V. All rights reserved.