Solid-phase synthesis of L10-FePd(001) epitaxial thin films: Structural transformations and magnetic anisotropy

The solid-phase synthesis of the L1₀-FePd magnetically hard phase in Fe(001)/Pd(001) epitaxial films has been experimentally investigated. The formation of three types of L1₀-FePd ordered crystallites whose c axes coincide with the ⟨;100⟩ directions of the MgO(001) substrate begins at the Fe/Pd interface at a temperature of 450°C. After an increase in the annealing temperature to 500°C, structural rearrangement occurs and gives rise to the predominant growth of L1₀-FePd crystallites with the c axis perpendicular to the film plane. After 10-h annealing, the fraction of such crystallites becomes dominant, leading to large perpendicular anisotropy. The first magnetocrystalline-anisotropy constant of the L1₀-FePd phase has been determined and the second constant has been estimated. It has been shown that magnetic anisotropy in the L1₀-FePd(001) basal plane cannot be described by the biaxial anisotropy of the tetragonal crystal. The annealing above 500°C results in the evolution of L1₀-FePd to a disordered cubic phase.