Suppression of 90° spin switching in Co nanomagnets grown on the Cu(110)-{2x1}O surface

We report on the effect of oxygen on the CO-induced 90 degrees spin switching in the Co/Cu(110) system [Hope , Phys. Rev. B 57, 7454 (1998)]. The epitaxial fcc Co films were grown on the unsaturated Cu(110)-{2 x 1}O surface and their magnetic properties have been studied with in situ magneto-optic Kerr effect. The easy axis switch of the Co(110) films is suppressed when Co is grown on O exposed Cu surfaces. Scanning tunneling microscopy images of the film surface reveals the growth of elongated nanostructures preferentially oriented along the [001] direction, providing step-like edges for gas adsorption. The density of steps is similar to the density developing during growth on the clean Cu(110) surface but the step edges now run in the perpendicular direction. The suppression of the easy axis switch can be attributed to subtle changes of the number and adsorption probability of the available atop adsorption sites along the step edges for CO chemisorption. Our experiments highlight the remarkable chemical sensitivity and adsorption site dependence of the easy axis switch of the Co(110) nanomagnets. (C) 2001 American Institute of Physics.