Thickness-dependent Curie temperature of Gd(0001)/W(110) and its dependence on the growth conditions

The Curie temperature TC of 5--100 monolayers Gd is determined by in situ ac-susceptibility (χac) measurements. TC of properly annealed layer-by-layer-grown Gd films decreases as a function of film thickness in the same way as is usually found from finite-size effects in other ferromagnets. Sharp cusps in the susceptibility as a function of temperature are measured. The shape of the χac signal and the Curie temperature is strongly dependent on the growth mode and on the annealing procedure after deposition at room temperature. These results are compared to our earlier experiments on Gd films grown at elevated substrate temperatures.