Magnetic and structural properties of annealed CoPt/C multilayers

The structure and magnetic properties of multilayer CO82Pt18/C films with equal CoPt and C layer thickness have been studied as a function of annealing temperature and film thickness. In general, annealing leads to the breakup of the continuous films and the formation of a laterally heterogeneous morphology consisting of separate CoPt and C regions. For individual layer thickness greater than or equal to 5.3 nm, annealing has no significant effect on the crystallographic structure and magnetic properties of the films. In both the as-deposited and annealed states, the films have HCP structure with perpendicular c-axis orientation and exhibit perpendicular magnetic anisotropy. The structure of these films appears to be associated with the growth of the CoPt on the C layers. For films with individual layer thickness of 1.3 and 2.7 nm, the structure and magnetic properties are strongly affected by annealing. In the as-deposited state, films have a fine grain structure and coercivities of a few Oe. Annealing leads to the breakup of the multilayer structure at about 300 degreesC and the formation of similar to 20nm HCP and FCC magnetic grains, with the HCP grains exhibiting in-plane c-axis texture. Annealed films have large in-plane coercivities (maximum of 2.77 kOe) and random in-plane magnetic anisotropy. The increase in coercivity with annealing temperature above similar to 375 degreesC is primarily associated with an increase in switching volume. (C) 2001 Elsevier Science B.V. All rights reserved.