Improvement in hard magnetic properties of FePt films by introduction of Ti underlayer

The FePt/Ti double layer films were prepared by dc magnetron sputtering on corning glass substrates with FePt and Ti targets. The Ti underlayer with 100-nm thickness was deposited at substrate temperature 200°C, and the FePt magnetic layer, 300 nm, was prepared at temperature from 200°C to 600°C for direct formation of ordered L1₀ FePt phase on the Ti underlayer. X-ray diffraction analysis showed that the [002] axis of Ti grain was perpendicular to the film plane and the FePt grains had a preferred growth of (111) plane parallel to the film plane. The degree of ordering of the FePt films increased as Ti underlayer was introduced. Magnetic property measurements indicated that the in-plane coercivities (Hc_||) of the FePt/Ti films in which FePt films was deposited at different temperatures were all higher than that of FePt single layer film without Ti underlayer. When the deposition temperature of FePt film was fixed at 600°C, the Hc_|| value of the FePt single layer film was 3.1 kOe, and it increased to 7.3 kOe as 100 nm Ti underlayer was introduced.