Impact of Boron Additions on the A1 to L1$_{0 }$Phase Transformation in FePt Alloy Films

The combination of high magnetocrystalline anisotropy energy density and good corrosion resistance has resulted in significant interest in L1$_{0}$ ordered alloys such as FePt for ultrahigh density, heat assisted magnetic recording (HAMR) media, with areal storage densities of $\ge $1Tb/in$^{2}$. When deposited at room temperature, these FePt forms in the chemically-disordered A1 state, requiring a post-deposition anneal to form the ordered L1$_{0}$ phase. Previous work has shown that the composition of FePt films has a significant impact on the kinetics and thermodynamics of the A1 to L1$_{0}$ phase transformation. In this paper, we report on the impact of ternary additions of B to FePt on the thermodynamic and kinetic parameters of the transformation. We also compare and contrast the impact of B additions with those of ternary additions of Cu and Ni. It is shown that the introduction of B into Pt-rich FePt films lowers the activation energy and the kinetic ordering temperature for the A1 to L1$_{0}$ phase transformation. However, this impact becomes negligible when B is introduced into Fe-rich FePt films.