Structure and Magnetic Properties of CoPt, CoPd, FePt, and FePd Alloy Thin Films Formed on MgO(111) Substrates

CoPt, CoPd, FePt, and FePd alloy thin films are deposited on MgO(111) single-crystal substrates by using a radio-frequency magnetron sputtering system. The effects of magnetic material and substrate temperature on ordered phase formation are investigated. CoPt, FePt, and FePd epitaxial films with the close-packed plane parallel to the substrate surface are obtained at substrate temperatures ranging between room temperature (RT) and 600 ^°C. CoPd films grow epitaxially at temperatures higher than 200 ^°C, whereas CoPd amorphous films are formed below the temperature. Metastable L1₁ ordered phase formation is recognized for the CoPt films prepared at temperatures ranging between RT and 400 ^°C. As the temperature increases from RT to 300 ^°C, the order degree of L1₁ phase increases. With further increasing the temperature, the degree declines. The CoPt films formed above 500 ^°C are with A1 disordered structure. L1₀ ordered FePt and FePd films with the c-axis 55 ^° canted from the perpendicular direction are obtained at 600 ^°C, whereas A1 disordered FePt and FePd films are formed below the temperature. No ordered phase is formed in CoPd film. The L1₁ ordered CoPt films show perpendicular magnetic anisotropies. As the order degree of L1₁ phase increases, perpendicular anisotropy is enhanced. On the contrary, the L1₀ ordered FePt and FePd films have in-plane anisotropies. The magnetic properties are influenced by the kind of ordered phase and the order degree.