Magnetic property enhancement of Fe49-xCoxPt51 (x=0.0,0.7,1.3,2.2) thin films

Magnetic properties of Fe_49-xCo_xPt₅₁ (x=0.0,0.7,1.3, and 2.2) thin films are investigated. Cobalt is found to enhance the magnetization and energy product of the films. A maximum energy product of 18.4 MGOe is obtained at x=1.3. This value is 87% larger than that of a binary FePt film. High-saturation magnetization of M_s=1180 emu/cm³ and remanent magnetization of M_r=862emu/cm³ are obtained as the sample with x=1.3 was annealed at 500°C. The addition of cobalt increases the ordering temperature of the film, which retains more disordered phase in the film and thus produces higher magnetization than the binary sample. Exchange coupling is found to exist between ordered and disordered FePt phases. The intensive intergranular exchange coupling also makes the switching of magnetic moments in the thin film more cooperative. We consider that both the magnetization enhancement and the cooperated switching behavior in the thin film are responsible for the increased energy product.