Atomic resolution strain analysis in highly textured FePt thin films

In this work, we present a detailed investigation of FePt-substrate interfaces and their influence towards the microstructural and magnetic configurations of the resulting metallic films. Discontinuous FePt films of roughly 15 nm thickness are deposited at 750 °C on MgO, MgAl2O4, SrTiO3, and (La,Sr)(Al,Ta)O3 single-crystalline substrates. All of these films mainly show out-of-plane textured FePt islands; however, fractions of L12 and in-plane oriented crystals are observed for the films on substrates with reduced lattice mismatch. Reduced easy axis coercivities and enhanced hard axis remanence values affirm this observation. Moreover, quantitative high-resolution transmission electron microscope analysis reveals that the reduced lattice mismatch results in a decreased density of dislocations, especially misfit dislocations, at the FePt-substrate interface. To further extend the research, carbon-doped FePt+32%C films are deposited on single-crystalline and sputtered MgO at 750 °C and 650 °C, respectively, to characterize the influence of a segregating media and reduced grain size. A comparison to the pure FePt sample reveals that the presence of seed layer grain boundaries leads to an increased fraction of in-plane oriented material, while the density of misfit dislocations solely depends on the degree of lattice mismatch.