Investigation of microstructure and magnetic properties of FePt–X films grown on MgO and STO substrates

• Different lattice mismatch resulted in different microstructure.
• Doping SiNx and C into FePt films caused the increase of lattice mismatch strain.
• Negligible mismatch strain with using STO substrate would form continuous film.
• The larger mismatch strain with using MgO substrates would form granular film.

Different thickness (001) textured FePt–X films were fabricated on MgO and SrTiO3 substrates, and the microstructure and magnetic properties of FePt–X films was systematically investigated. The study showed that the substrates with different lattice mismatch resulted in different crystallographic texture and microstructure. The larger mismatch strain with using MgO substrates would cause FePt films to follow the island growth mode, and the negligible mismatch strain with using STO substrate would form continuous film. Doping SiNx and C into FePt films caused the increase of lattice mismatch strain between FePt and MgO/STO, which would induce FePt films to forming island growth. The perpendicular anisotropy of FePt–SiNx–C films grown on MgO substrate was larger than that of using SrTiO3 substrate, which was attributed to the larger strain induced by larger lattice mismatch.