Microstructural and magnetic studies of L10 FePt–SiO2 nano-composite thin film with columnar structure for perpendicular magnetic recording

(Fe50Pt50)100−x-(SiO2)x films (x=0–30 vol%) were grown on a textured Pt(0 0 1)/CrRu(0 0 2) bilayer at 420 °C using glass substrates. FePt(0 0 1) preferred orientation was obtained in the films. Interconnected microstructure with an average grain size of about 30 nm is observed in the binary FePt film. As SiO2 is incorporated, it precipitates as particles are dispersed at FePt grain boundaries. When the content of SiO2 is increased to 13 vol%, columnar FePt with (0 0 1) texture separated by SiO2 is attained. The FePt columns have a length/radius ratio of 2:1. Additionally, the mean grain size is reduced to about 13 nm. The development of this well-isolated columnar structure leads to an enhancement in coercivity by about 44% from 210 to 315 kA/m. As the SiO2 content exceeds 20 vol%, a significant ordering reduction is found accompanied by a transformation of preferred orientation from (0 0 1) to (2 0 0) and the columnar structure disappears, resulting in a drastic degradation in magnetism. The results of our study suggest that isolated columnar, grain refined, (0 0 1)-textured FePt film can be achieved via the fine control of SiO2 content. This may provide useful information for the design of FePt perpendicular recording media.