Preparation of CoPt-Alloy Thin Films With Perpendicular Magnetic Anisotropy on MgO(111), SrTiO3(111), and Al2O3(0001) Single-Crystal Substrates

Co50Pt50 (at. %) alloy thin films are prepared on MgO(111), SrTiO3(111), and Al2O3(0001) single-crystal substrates by ultra-high vacuum radio-frequency magnetron sputtering by varying the substrate temperature from room temperature to 600 degrees 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 SrTiO3 substrates. On Al2O3 substrates, CoPt epitaxial films are obtained at temperatures higher than 500 degrees C, whereas CoPt films consisting of epitaxial and polycrystalline crystals are formed below 400 degrees C. From the view points of order degree and stacking sequence of close-packed plane along the perpendicular direction, the crystal structure is determined. L1(1) ordered phase is preferentially formed and is stabilized around 300 degrees C for all the employed substrate materials. A higher order degree is observed for the films prepared on MgO > SrTiO3 > Al2O3. The magnetic properties are influenced by the crystal structure and the order degree.