Structure and magnetic property of c-axis oriented L1₀-FePt nanoparticles on TiN/a-Si underlayers

L1₀-FePt is a promising material for high-density perpendicular magnetic recording media. The authors previously reported that c-axis oriented L1₀-FePt nanoparticle monolayers can be formed on (200)-oriented polycrystalline template TiN underlayers on SiO₂ by using a conventional sputtering method. In this study, TiN nanostructures, such as the degree of (200) orientation, were improved by first depositing a buffer layer, such as amorphous Si onto SiO₂, and the grain size could be controlled by adjusting either the deposition temperature or TiN thickness. When FePt nanoparticles were formed on a template TiN underlayer with a buffer layer of amorphous Si, both their degree of c-axis orientation and their magnetic properties were improved; FePt nanoparticles with nominal thickness of 1.4 nm had coercivity of 12.9 kOe in the out-of-plane direction at 300 K.