Magnetic and structural properties of epitaxial cobalt-platinum alloy films

Epitaxial Co₈₀Pt₂₀ films with c-axis in-plane have been sputtered on H-terminated Si(110) substrates with Ag(110)/Cr(112) or Ag(110)/W(112) templates. The residual epitaxial strains were measured by x-ray diffraction. Uniaxial anisotropy constants were measured and correlated to the epitaxial strains (magnetoelastic effects). The magnetoelastic coupling constants and magnetostriction were also directly measured. However, it was found that magnetoelastic effects alone could not explain the change in anisotropy constants of Co₈₀Pt₂₀ films over a range of thickness.; The coercivity of as-deposited CoCrPt films is low because the switching is dominated by domain wall motion. After the CoCrPt films were annealed in a high vacuum, the coercivity increased and the magnetization decreased. The switching mechanism changed from domain wall motion to non-coherent rotation. MFM images reveal that magnetic clusters formed after the CoCrPt films were annealed. However, there are no changes in surface morphology, grain size, or crystal orientation in CoCrPt films after annealing. Composition analysis shows W diffused into the CoCrPt layer, which changed the average film composition from Co₇₂Cr₁₄Pt₁₂W₂ to Co ₆₃Cr₁₃Pt₁₄W₁₀. Composition variation in Co, Cr, and W was found in the CoCrPt layer before and after annealing. The composition variation was not grain boundary related. The changes in magnetic properties can not be explained by grain boundary diffusion but are likely related to the magnetically induced miscibility gap in the CoCrPt phase diagram.