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

Abstract

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.