[en] We carried out ion-beam mixing of ferromagnetic multilayered films and investigated their electronic structures and magnetic properties for the purpose of modifying their magnetic properties. For this study, the [Pt(4.5 nm)/Co(3.5 nm)] x 8 multilayered films were prepared on Si (100) substrates by alternating electron-beam evaporation and were ion-beam mixed with 80 keV Ar⁺ in a high vacuum. The electronic structures and the magnetic moments of the samples were investigated using X-ray emission spectroscopy and magnetic circular dichroism, respectively. In addition, X-ray diffraction was used to confirm the atomic structures before and after ion-beam mixing. The experimental results for our samples showed a significant enhancement of the magnetic moment after ion-beam mixing with respect o to those of unmixed Co/Pt multilayered and stable equiatomic CoPt alloy films