Morphology evolution and magnetic properties improvement in FePt epitaxial films by in situ annealing after growth

This paper presents a detailed study of structure, morphology, and magnetic properties in FePt thinfilms epitaxially grown on MgO100 at intermediate temperatures 380 °C. It focuses on theeffects obtained by in situ annealing the FePt films after deposition. We have demonstrated that theannealing allows one to complete the ordering, thus obtaining an epitaxial L10-FePt film with largeperpendicular anisotropy up to 3107 erg/cm3 and high perpendicular squareness and remanenceratio both higher than 0.85. At the same time, we have found a peculiar morphology evolution byincreasing the annealing time: the interconnected mazelike grains evolve towards interconnecteddotlike grains of reduced size down to 10 nm. Due to the interconnection at the grains basis, theincrease in the film perpendicular coercivity with the annealing process is moderate up to 4.1 kOe,leading to an increasing anisotropy/coercivity ratio with the annealing time. As a further steptowards the understanding of the properties evolution with annealing, we have investigated themagnetic domain pattern and analyzed the domain-period dependence on the anisotropy constant incomparison with the behavior expected by the Kooy–Enz theory C. Kooy and U. Enz, Philips Res.Rep. 15, 7 1960. The main magnetic properties and reduced grain size obtained after the in situannealing are promising to realize perpendicular recording media with reduced bit size, high thermalstability, and suitable switching field.