Thickness dependence of (001) texture evolution and magnetic properties of sputter-deposited FePt: MgO nanocomposite films

We investigate the effect of the number of bilayers (total film thickness) on the (001) texture development, L1₀ordering reaction and magnetic properties in multilayered [FePt/MgO]₆ films that were sputter deposited on thermally oxidized Si substrates. We obtained nearly perfectly L1₀ (001) oriented nanocomposite films when the initial multilayer structure was [FePt 2.8 nm/MgO 3.2 nm]₆ and the total film thickness was 36 nm. When the film thickness was thicker than about 36 nm or the film was overaged, the grain orientation of the film developed in a random direction. The evolution of the (001) texture was favorable when the total film thickness was thin enough for the strain generated during the ordering transformation to relax in the plane normal direction, thus satisfying the plane stress condition. In addition, the disordered fcc FePt (200) texture grown on (200)-textured MgO in the as-deposited state also affected the L1₀ (001) texture evolution.