EVIDENCE FOR DOMAIN FORMATION NEAR THE CURIE-TEMPERATURE IN ULTRATHINNI CU(001) FILMS WITH PERPENDICULAR ANISOTROPY/

Ni films, 8-10 monolayers thick on a Cu(001) substrate, are studied in UHV by the polar magneto-optic Kerr effect near the Curie temperature T-C. The films are magnetized normal to the surface. An unusual sharp drop of the remanent magnetization (M-r) and a large difference of ab out 10 K are measured between the temperature T-r at which M-r and the temperature T-H at which the magnetization M(H) in a static field of 20 G vanishes. We show that at T-r the films break up into ferromagnet ic domains with perpendicular magnetization components and that T-C is larger than T-r. The true T-C is deduced from field-dependent magneti zation measurements.