Tailoring magnetocrystalline perpendicular anisotropy in Co60Fe40/Pt multilayers

Highlights: • Magnetron sputtered CoFe/Pt multilayers with perpendicular magnetic anisotropy. • Control of Pt buffer layer growth allows tuning the anisotropy field. • Anisotropy enhanced by magnetocrystalline effects instead of lattice relaxation. • Magnetic properties compatible with spintronic applications. We report on the investigation of perpendicular magnetic anisotropy in magnetron sputtered Pt/[Co₆₀Fe₄₀/Pt]₅ multilayers, and the behaviour of the anisotropy field as function of the growth rate of the Pt buffer layer (4 nm thick). Highly crystallized, atomically flat (1 1 1) fcc-textured [CoFe/Pt] multilayers were obtained, as confirmed by high resolution transmission electron microscopy along with fast Fourier transform patterns and X-ray diffraction. Equivalent lattice relaxation between the Pt buffer and the CoFe/Pt multilayer was observed in all samples, indicating that the magnetic anisotropy is not dominated by magnetoelastic effects. Our results indicate that the formation of an ordered phase of CoFePt with fcc (1 1 1) texture, which is affected by the Pt buffer layer growth rate, regulates the anisotropy field in these multilayer systems, suggesting a magnetocrystalline origin of the observed perpendicular anisotropy. An optimum growth rate of the Pt buffer layer was obtained (∼0.7 Å/s), which allows enhancing the fcc (1 1 1) texture of the alloy-like CoFe/Pt multilayer, for which an uniaxial anisotropy energy constant of 3.5 × 10⁶ erg/cc and an anisotropy field of 13 kG were obtained.