Microstructure and magnetic properties of FePt(B4C) and FePt(B4C-Ag) granular films with perpendicular magnetization

Multilayers [FePt/B4C (t nm)]10 (t = 0-0.4) and [FePt/(B4C)yAg1−y (0.1 nm)]10 (y = 0.2-0.8) films were deposited on a glass substrate and subsequently annealed by a rapid thermal process (RTP) at 800 °C for 3 min. After RTP, the granular FePt(B4C) and FePt(B4C-Ag) films with perpendicular magnetization were formed. The FePt grains were interconnected in FePt(B4C) films and further broken into the small round grains in FePt(B4C-Ag) films. In FePt(B4C) films, the maze-like structure with worm shape FePt grains but the grains boundaries were still defined. The granular structure with well defined boundaries was formed when the minor Ag was added to partial replace B4C. The immiscible (B4C, Ag) were demonstrated as segregant to separate FePt grains without affecting c-axis alignment. The FePt grains were separated uniformly with size distribution 19% and the average grains size was 13.5 nm in (Fe0.48Pt0.52)90 [(B4C)0.6Ag0.4)]10 film. The average grains size of FePt was 10. 6 nm in (Fe0.48Pt0.52)90 [(B4C)0.2Ag0.8)]10 film. The grains were more distanced and show magnetostatic coupling.