Magnetic and structural properties of annealed CoPt/C multilayers

The structure and magnetic properties of multilayer CO82Pt18/C films with e qual CoPt and C layer thickness have been studied as a function of annealin g temperature and film thickness. In general, annealing leads to the breaku p of the continuous films and the formation of a laterally heterogeneous mo rphology consisting of separate CoPt and C regions. For individual layer th ickness greater than or equal to 5.3 nm, annealing has no significant effec t on the crystallographic structure and magnetic properties of the films. I n both the as-deposited and annealed states, the films have HCP structure w ith perpendicular c-axis orientation and exhibit perpendicular magnetic ani sotropy. The structure of these films appears to be associated with the gro wth 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 affec ted by annealing. In the as-deposited state, films have a fine grain struct ure and coercivities of a few Oe. Annealing leads to the breakup of the mul tilayer structure at about 300 degreesC and the formation of similar to 20n m HCP and FCC magnetic grains, with the HCP grains exhibiting in-plane c-ax is texture. Annealed films have large in-plane coercivities (maximum of 2.7 7 kOe) and random in-plane magnetic anisotropy. The increase in coercivity with annealing temperature above similar to 375 degreesC is primarily assoc iated with an increase in switching volume. (C) 2001 Elsevier Science B.V. All rights reserved.