Ordering of island-like FePt L10 thin films

We report the island growth morphology of 50-nm-thick FePt thin films prepared on MgO substrates by dc magnetron sputtering. In-depth high-resolution transmission electron microscopy studies showed that the island had a very flat facet in a dome shape and was composed of two distinct structures. The island contained FePt grains with an average size of 5–7 nm within about 10 nm from the film surface, whereas an ordered ${\text{L1}}_0$ phase was established below the island. The ${\text{L1}}_0$ structure was compressively strained along the film plane, generating {111} twins and stacking faults. The strained structure also affected the region where agglomeration between islands occurs.