JMMM 93 (1991) 571-586
Invited paper
Phenomenology of anisotropy in the ferromagnetism of ultrathin films
Anthony S. Arrot and Bretislav Heinrich

The role of anisotropy in the micromagnetics and the dynamic response of
the magnetization of ultrathin films is explained for a nonspecial
audience. The energetics of domain walls are used to introduce the
parameters of micromagneticsm. The arguments why demagnetizing fields do
not cause domains in ultrathin films are restated. It is shown that in the
absence of anisotropy large nonlinear fluctuations would destroy the
magnetic order. Brown's paradox is discussed. Particular emphasis is
placed on the effects of pinning sites on the static magnetic
response. It is shown how pinning sites can cause the surface to show a
magnetic response that differs from that a few nanometers away from the
surface. The creation of a freely moving domain wall from the interaction
of a pair of pinning sites is demonstrated. The temperature dependence of
the magnetization from spin wave excitations is calculated from ultrathin
films. In each case the mathematics is provided.