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

摘要

${rm Co}_{50}{rm Pt}_{50}$ (at. %) alloy thin films are prepared on MgO(111), ${rm SrTiO}_{3}(111)$, and ${rm Al}_{2}{rm O}_{3}(0001)$ single-crystal substrates by ultra-high vacuum radio-frequency magnetron sputtering by varying the substrate temperature from room temperature to 600$^{circ}{rm C}$ . 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 ${rm SrTiO}_{3}$ substrates. On ${rm Al}_{2}{rm O}_{3}$ substrates, CoPt epitaxial films are obtained at temperatures higher than 500$^{circ}{rm C}$, whereas CoPt films consisting of epitaxial and polycrystalline crystals are formed below 400$^{circ}{rm C}$. 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$^{circ}{rm C}$ for all the employed substrate materials. A higher order degree is observed for the films prepared on ${rm MgO}>{rm SrTiO}_{3}>{rm Al}_{2}{rm O}_{3}$. The magnetic properties are influenced by the crysta- structure and the order degree.