Magnetic behavior of thin rare-earth films

We consider a thin rare-earth film with the c axis perpendicular to the surface, to study its nonuniform magnetic structure induced by the lower coordination near the surfaces. The influence of a de magnetic field, applied perpendicular to the c axis, on the equilibrium configurations is also investigated. The spin-wave frequencies, in the q=0 limit, are calculated as a function of the strength of the external de field. We use the bulk parameters of dysprosium and holmium to obtain the external field dependence of the equilibrium configuration, magnetization, and the lowest spin-wave modes of 30-monolayer-thick films. [S0163-1829(99)10209-1].