Ie. Dikshtein et Sa. Nikitov, INHOMOGENEOUS SURFACE AND VOLUME MAGNETIC STATES IN FERROMAGNETIC-FILMS CLOSE TO THE CURIE-TEMPERATURE, Journal of magnetism and magnetic materials, 153(1-2), 1996, pp. 151-183
We present a theory of nucleation of one- and two-dimensional lattices
of surface and volume domains in ferromagnetic films close to the Cur
ie point in a magnetic field normal to the film surface. A class of un
iaxial ferromagnetic films with the 'easy axis' perpendicular to the s
urface is considered. It is shown that in thick ferromagnetic films wi
th a positive surface energy of exchange origin at a temperature excee
ding the temperature of the inhomogeneous volume magnetic state nuclea
tion, the paramagnetic phase becomes unstable with respect to the surf
ace domain structure nucleation. The critical value of the surface ene
rgy for the surface domain nucleation is found. A phase transition fro
m the surface domain structure to the volume structure is a first-orde
r phase transition. In thin films a set of phase transitions (paramagn
etic phase --> volume domain structure --> paramagnetic phase) is pred
icted with increasing film thickness. The existence of such a transiti
on is entirely controlled by the surface energy. A phase diagram of th
e inhomogeneous surface and volume states is constructed and the param
eters of the nucleating surface and volume domains are defined. The ef
fect of magnetization fluctuations on the results obtained is discusse
d.