CURIE-TEMPERATURE AND MORPHOLOGY IN ULTRATHIN CO W(110) FILMS/

The magnetic properties of ultrathin Co films grown on W(110) were stu died as a function of Co thickness (1-5 monolayers), substrate tempera ture during the growth (170 K less than or equal to T-s less than or e qual to 420 K), and annealing temperature (T-an, 800 K) for films grow n at room temperature. Magnetic results are obtained by means of in si tu magneto-optical Kerr effect in static fields and small oscillating fields. The Curie temperature T-C of 1.4-2 monolayers varies linearly from 160 to 450 K. No change of this behavior is found for depositions at 170 K<T-s<370 K. Furthermore, we measure a large ac susceptibility chi(max)approximate to 3000. This indicates the good magnetic homogen eity of the film. Layers annealed to T-an>440 K show a much lower T-C and a reduced chi(max). Deposition at T-s>420 K yields the same behavi or. This is correlated to changes in the morphology of the Co layers a s observed by Auger spectroscopy.