The temperature-dependent magnetic properties of Gd(0001)/W(110) films
were investigated using the magneto-optical Kerr effect. Measurements
of hysteresis loops, remanent magnetization, and susceptibility were
performed as a function of temperature and film thickness (d = 10-130
nm). Well annealed films of sufficient thickness (d greater than or eq
ual to 40 nm) show an anomalous temperature dependence of the coercive
field H-c(T) and the remanent magnetization M(r)(T). In addition, a s
econd peak in the in-plane as well as out-of-plane susceptibility was
observed for these films. All experimental results for thick films can
consistently be explained by a reorientation transition between a low
-temperature phase with uniform inplane magnetization and a high-tempe
rature phase with ii nonvanishing out-of-plane magnetization component
. The thickness dependence of the transition temperature T-r, as well
as the absence of a remanent out-of-plane magnetization implies that t
he reorientation transition is associated with the formation of a doma
in structure.