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
L
1
₁
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
L
1
₁
phase increases. With further increasing the temperature, the degree declines. The CoPt films formed above 500
^°
C are with
A
1 disordered structure.
L
1
₀
ordered FePt and FePd films with the
c
-axis 55
^°
canted from the perpendicular direction are obtained at 600
^°
C, whereas
A
1 disordered FePt and FePd films are formed below the temperature. No ordered phase is formed in CoPd film. The
L
1
₁
ordered CoPt films show perpendicular magnetic anisotropies. As the order degree of
L
1
₁
phase increases, perpendicular anisotropy is enhanced. On the contrary, the
L
1
₀
ordered FePt and FePd films have in-plane anisotropies. The magnetic properties are influenced by the kind of ordered phase and the order degree.