Study of microstructure and magnetic properties of L1₀ FePt/SiO₂ thin films

Department of Materials Science, INN, NCSR Demokritos, 153 10 Aghia Paraskevi Attikis, Athens, Greece

^a Corresponding author: gyian@ims.demokritos.gr

Published online: 3 July 2014

Abstract

Achieving magnetic recording densities in excess of 1Tbit/in² requires not only perpendicular media with anisotropies larger than 7 MJ/m³, making FePt alloys an ideal choice, but also a narrow distribution below 10 nm for a reduced S/N ratio. Such grain size reduction and shape control are crucial parameters for high density magnetic recording, along with high thermal stability. Previous work has shown that the L1₀ FePt grain size can be controlled by alloying FePt with materials such as C, Ag, and insulators such as AlO_x, MgO. Au and Al₂O₃ also act to segregate and magnetically decouple the FePt grains. Better results were obtained with C with respect to the uniformity of grains and SiO₂ with respect to the shape. We present our results on co-sputtering FePt with C or SiO₂ (up to 30 vol %) on MgO (001) single crystal substrates at 350 and 500 ^oC. With C or SiO₂ addition we achieved grain size reduction, shape control and isolated structure formation, producing continuous films with high uniformity and a narrow grain size distribution. These additions thus allow us to simultaneously control the coercivity and the S/N ratio. We also will report structural and microstructural properties.