Size effects on magnetic anisotropy of NPs

Chemical order and size effects on the magnetic anisotropy of FePt and CoPt nanoparticles.
Stanislas Rohart, Florent Tournus, Véronique Dupuis 
http://arxiv.org/abs/1105.6292

Statistical distribution of the easy magnetization
axis for a 201 atom FePt cluster, represented in
a 3D view along the [111] direction.

Variation of the anisotropy constant K1
versus |S| for a 201 atoms FePt (a) and CoPt (b) cluster, and
for a 2406 atoms FePt (c) and CoPt (d) cluster.