L11-CoPt(1 1 1) films were successfully fabricated on glass substrates at 300–400 °C, using Pt(1 1 1) underlayer. Magnetocrystalline anisotropy energy shows a maximum of 1.8 × 106J/m3at 350 °C. The mechanism of L11-CoPt ordering after introducing Pt underlayer is considered to be strain- or stress-induced ordering. The effect of CoPt layer thickness on phase structure and magnetic properties were investigated to confirm the ordering mechanism. Perpendicular magnetic anisotropy has been obtained in all CoPt films, while the squareness ratio and coercivity decrease with increasing film thickness, indicating decreased ordering due to the relaxation of strain or stress in thick films.