Microstructures and Magnetic Properties of ${\rm CoPt{-}SiN}_{x} {-}{\rm Ag}$ Granular Thin Films With Ag Underlayer

When the Ag layer was introduced under the CoPt alloy film which annealed at 700°C, the CoPt/Ag films had large out-of-plane squareness (S_⊥), out-of-plane coercivity (H_c⊥), and saturation magnetization (M_s). They were 0.95, 1432 kA/m, and 390 emu/cm³, respectively. Further, the SiN_x ceramic materials were cosputtered with CoPt on the Ag underlayer at room temperature and then annealed to reduce the grain size of CoPt films. From the field-emission gun high-resolution transmission electron microscope analysis, the particle size of CoPt was about 10 nm as the SiN_x content was 46.2 vol.%. Furthermore, Ag was added into the CoPt-SiN_x films to reduce the transformation temperature of CoPt films from face-centered-cubic to face-centered-tetragonal structure.