## Interface and Volume Anisotropy

It has been shown[18] that in multilayers the effective magnetic anisotropy energy, , can be phenomenologically split into two components: a volume contribution, , and an interface contribution, , which are related to by

 (5.2)

where is the thickness of the magnetic layer. The relation is a weighted average of the magnetic anisotropy energy of the interface atoms and the inner volume'' atoms in the layer. The factor of 2 arises from the layer being bounded by two interfaces.

In bulk systems the magnetocrystalline anisotropy of a system is dominated by the volume term. In thin films and multilayers, however, the surface term can become more significant as becomes small ( ). In most cases the anisotropy in thin magnetic layers is dominated by the dipolar shape anisotropy, favouring inplane moment alignment.

Dr John Bland, 15/03/2003