Effect of Carbon Mixing on the Perpendicular Magnetization of FePt Thin Film on Pt/MgO(p) Underlayer

The effect of carbon mixing on the perpendicular magnetization of magnetron sputtered FePt thin films on our newly developed underlayer of Pt/MgO(p) composite thin-film was studied using magnetic property measurement and X-ray diffraction, and TEM microscopy. Micromagnetic simulation was carried out to study the effect of texture on the perpendicular coercivity. Unlike a general expectation, the mixing of FePt with carbon led to a significant enhancement in the perpendicular magnetization. The maximum enhancement of perpendicular magnetization was observed at about 22 vol.% of carbon, where carbon amorphous film started to completely enclose the individual FePt grains. This was because the epitaxial growth and thus perpendicular texture of ordered FePt grains were maximized in the isolated grain structure due to a maximum relaxation of coherency strain for epitaxial growth. The simulation showed that the enhancement of perpendicular texture can largely increase the perpendicular coercivity of FePt:C thin film.