Variation of structure and magnetic properties by Ag addition in (001) oriented CoPt and CoPd alloy film

Tetragonal L1₀ phase magnetic materials, e.g., FePt and CoPt, have been extensively studied as potential candidates for future high-density perpendicular recording media. However, for the practical application of these materials, there still remain challenges such as fabrication of nano-sized grains, control of (001) orientation, and lowering the ordering temperature of L1₀ phase. One of the effective ways to realize these requirements is the addition of the third element, and Ag is known to be one of the effective elements to tailor the magnetic properties and ordering temperature of L1₀-FePt [1-3]. We have previously studied the effect of Ag addition in L1₀-FePt and L1₀-FePd, and found a significant difference in the effect of Ag addition between FePt and FePd; for FePt, Ag addition enhanced the coercivity and promoted L1₀ ordering, while for FePd, Ag addition lowered the coercivity. In this study, CoPt-Ag and CoPd-Ag systems have been studied in detail for the systematic understanding of the effect of Ag addition in 3d transition metal and noble metal alloy films.