Abstract
A study on the structural and magnetic properties of 5-nm-thick Co–Pt alloy films grown on thermally oxidized SiO2/Si(100) substrates as well as on self-assemblies of spherical SiO2 particles with sizes down to 10 nm is presented. An out-of-plane easy axis of magnetization was stabilized at deposition temperatures as low as 250 °C in a broad composition range between 40 and 70 at. % of Pt. Owing to the low deposition temperatures, no chemical long-range order is found. Thus, the strong out-of-plane magnetic anisotropy is expected to be caused by anisotropic short-range order effects. The magnetic behavior of CoPt alloys with an equiatomic composition grown on arrays of SiO2 particles was found to be similar to those on planar substrates. Structural investigations using high-resolution transmission electron microscopy revealed that a continuous CoPt layer has been formed, covering the particle tops and connecting them. The magnetic CoPt caps exhibit an out-of-plane easy axis for all particle sizes; however, no pronounced difference in coercive field with particle size was observed, which is associated with the specific morphology of the film structure.
Highlights
For further increase in the storage density in magnetic hard disk drives, materials with high uniaxial out-of-plane magnetic anisotropy such as001͒ textured FePt or CoPt alloys are required to provide sufficient thermal stability for the written bits of information
5-nm-thick CoPt alloy films with an equiatomic composition were grown on amorphous SiO2 / Si100͒ substrates at various growth temperatures between room temperature and 415 ° C
It turns out that hard magnetic Co–Pt thin films with out-of-plane anisotropy can be formed at deposition temperatures as low as 250 ° C in a broad composition range between 40 and 70 at. % of Pt
Summary
For further increase in the storage density in magnetic hard disk drives, materials with high uniaxial out-of-plane magnetic anisotropy such as001͒ textured FePt or CoPt alloys are required to provide sufficient thermal stability for the written bits of information. A reduction in ordering temperature was reported for CoPt3͑111͒ thin films grown on a low energy surface of WSe2͑0001͒.9–11 In this case, a strong out-of-plane magnetic anisotropy is induced by a short-range anisotropic chemical order driven by Se segregation even for films grown at room temperature.. The physical origin of the short-range ordering resulting in the out-of-plane magnetic anisotropy is not yet clear In this regard, Maranville et al. performed kinetic Monte CarloMCsimulations on continuous CoPt3 films relating the out-of-plane magnetic anisotropy to the short-range order induced by clustering of Co due to its step-edge segregation during the deposition process. Maranville et al. performed kinetic Monte CarloMCsimulations on continuous CoPt3 films relating the out-of-plane magnetic anisotropy to the short-range order induced by clustering of Co due to its step-edge segregation during the deposition process This Co step-edge segregation does not depend on a particular growth direction. The combination of a template consisting of self-assembled nanoparticles with magnetic film deposition provides an elegant way of creating ordered arrays of nanostructures with welldefined magnetic properties. it was investigated how these film properties will be altered by depositing 5-nm-thick CoPt alloys with an equiatomic composition onto self-assemblies of spherical SiO2 particles with various particle sizes down to 10 nm
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