Response and enhancement of surface magneto-optic Kerr effect for Co-Pt(111) ultrathin films and surface alloy

Magnetic anisotropy as a function of Co coverage was comparatively studied on a flat and sputtered Pt(111) surface by a surface magneto-optic Kerr eff ect. The magnetic anisotropy of the flat Pt(111) surface changes gradually from out-of-plane to in-plane when the film thickness is over four monolaye rs, whereas both the out-of-plane and in-plane anisotropy occur on the sput tered Pt(111) surface. This difference is attributed to the fact that the m agnetocrystalline anisotropy is diminished from the sputtered surface. A la rge enhancement in the polar magnetooptic Kerr signal was observed after on e atomic layer of Co adatoms on the flat Pt(111) surface was annealed at 71 0 K. The formation of Co-Pt alloy at the interface following the enhancemen t was confirmed by low-energy electron diffraction and Auger electron spect roscopy. The mechanism of the enhancement is discussed. (C) 1999 Elsevier S cience B.V. All rights reserved.