Improvement of isolation and grain size of FePt-SiNx-C films with TiON intermediate layer

• With doping 40 vol.% TiO2 into TiN intermediate layer, a solid solution of f.c.c TiN and f.c.c TiO was formed.
• The lattice constant and surface energy of intermediate layer were reduced and interface energy was increased.
• With using TiON intermediate layer, FePt grain isolation and grain size uniformity were improved.

The effects of TiON intermediate layer on the microstructure and magnetic properties of FePt-SiNx-C films were systematically investigated. It is found that with using TiON intermediate layer, FePt grain isolation and grain size uniformity were improved. Moreover, the average grain size of FePt-SiNx-C films was significantly reduced from 8.77 ± 1.56 nm (480 °C) and 7.47 ± 1.55 nm (400 °C) with TiN intermediate layer to 6.41 ± 1.21 nm (480 °C) and 5.99 ± 1.0 nm (400 °C) with TiON intermediate layer, respectively. With doping 40 vol.% TiO2 into TiN intermediate layer, a solid solution of f.c.c TiN and f.c.c TiO was formed, which included 12.1 at.% titanium monoxide, 21.2 at.% titanium nitride and 66.7 at.% titanium oxynitride. Simultaneously, the lattice constant and surface energy of intermediate layer were reduced and interface energy was increased, which would cause the promotion of the island growth of FePt, thus the improvement of the isolation and the decrease of the FePt grains. The perpendicular magnetic anisotropy had a little deterioration with using TiON intermediate layer. This was attributed to lower crystallinity of TiON than pure TiN caused by a large number of vacancies in either Ti or N (O) lattice sites.