EFFECT OF INTERFACE ROUGHNESS ON HYSTERESIS LOOPS OF ULTRATHIN CO FILMS FROM 2 TO 30 ML ON CU(001) SURFACES

Ultrathin Co films have been grown on a smooth Cu(001) surface and a r ough Cu(001) surface by molecular beam epitaxy (MBE). Using high-resol ution low-energy electron diffraction (HRLEED) angular profile measure ment and a kinematic LEED model, we quantitatively extracted the inter face width w, the roughness exponent alpha(film) and the lateral corre lation length xi for Co films grown on a smooth Cu surface from 2 up t o 30 ML thick. Corresponding magnetic properties, including the Kerr i ntensity I-k, coercivity H-c and d[M]/dHI(/H=Hc) (the slope of the hys teresis loop at H = H-c) were obtained from hysteresis loops measured by the surface magneto-optic Kerr effect (SMOKE). For 2 to 7 ML thick Co films grown on the rough Cu surface the hysteresis loop shape is mu ch less square-like compared with that bf Co films grown on the smooth Cu surface; the Kerr intensity I-k is a factor of 3-4 smaller than th at of the smooth film; the H-c value is approximate to 3 times larger than that of the smooth him. H-c is almost thickness independent in th e 2-7 ML regime, in contrast to that of the smooth him in the same thi ckness region. The difference in magnetic properties can be qualtitati vely explained in terms of the quantitative roughness parameters assoc iated with the Co films. (C) 1997 Elsevier Science B.V.