REORIENTATION OF THE MAGNETIZATION AND THE CURIE-TEMPERATURE OF NI/CU(001) ULTRATHIN FILMS

Ni and Gd films are the two ferromagnets for which the change of the Curie temperature can be followed from infinitely thick films down to one monolayer. The difference of T-c for Ni(001) and Ni(111) is discussed in terms of different missing n.n. To measure T-c we propose the susceptibility rather than the magnetization, while ferromagnetic resonance is a unique technique to measure various contributions of the anisotropy energy also in higher order. From the separation of surface and volume contributions determined for 3 to 9 ML we estimate a flip of the easy axis of magnetization into perpendicular orientation for films above 7 ML. This is understood within a magnetoelasticity theory for a pseudomorphic Ni/Cu(001).