We investigate in this paper the origin of perpendicular anisotropy in Co (1.6 nm)/Pt (3.0 nm) bilayers grown on alumina and annealed up to 650∘C. Above 350∘C, all layers exhibit perpendicular anisotropy. Then coercive fields increase linearly with annealing temperature following two different rates: 0.05 T/100∘C below 550∘C and 0.8 T/100∘C above. By making careful structural characterizations using x-ray diffraction and transmission electron microscopy, we demonstrate the presence of short range correlation of L11 type below 550∘C whereas above 550∘C, L10 chemical ordering is observed. We conclude that perpendicular anisotropy observed in Co/Pt bilayers grown on alumina and annealed may not only be due to interface anisotropy as usually invoked but also to CoPt alloying and chemical ordering that take place during post-growth annealing.
@article{arxiv.1110.2628,
title = {Origin of perpendicular anisotropy in thin Co/Pt bilayers grown on alumina},
author = {L. Grenet and C. Arm and P. Warin and S. Pouget and A. Marty and A. Brenac and L. Notin and P. Bayle-Guillemaud and M. Jamet},
journal= {arXiv preprint arXiv:1110.2628},
year = {2011}
}