Preparation of CoPt-Alloy Thin Films With Perpendicular Magnetic Anisotropy on MgO(111), ${\rm SrTiO}_{3}(111)$, and ${\rm Al}_{2}{\rm O}_{3}(0001)$ Single-Crystal Substrates

Co
₅₀
Pt
₅₀
(at. %) alloy thin films are prepared on MgO(111), SrTiO
₃
(111), and Al
₂
O
₃
(0001) single-crystal substrates by ultra-high vacuum radio-frequency magnetron sputtering by varying the substrate temperature from room temperature to 600°C . Effects of substrate material and substrate temperature on the crystallographic and magnetic properties are investigated. CoPt-alloy epitaxial thin films with the close-packed plane parallel to the substrate surface are obtained on MgO and SrTiO
₃
substrates. On Al
₂
O
₃
substrates, CoPt epitaxial films are obtained at temperatures higher than 500°C, whereas CoPt films consisting of epitaxial and polycrystalline crystals are formed below 400°C. From the view points of order degree and stacking sequence of close-packed plane along the perpendicular direction, the crystal structure is determined.
L
1
₁
ordered phase is preferentially formed and is stabilized around 300°C for all the employed substrate materials. A higher order degree is observed for the films prepared on MgO >; SrTiO
₃
>; Al
₂
O
₃
. The magnetic properties are influenced by the crystal structure and the order degree.