The influence of the surface on the spontaneous magnetization of Gd thin films

Spin-polarized photoemission data on strained Gd(0001) films grown on Mo(112) are presented and explained in terms of an adequate mean-field approach. Experiment shows that the films exhibit a magnetic surface transition which occurs at about 10% above the bulk Curie temperature. The calculation yields an exponentially decaying surface magnetization mode whose penetration depth depends on the relative strengths of the interlayer exchange couplings J(tau - tau'). Second-order perturbation-theory refinements with respect to the long-range RKKY interactions yield a renormalization of the exchange between adjacent layers and small long-range magnetization contributions.