Published online by Cambridge University Press: 10 February 2011
We have studied the magnetic properties of the Co/Cu(110) system at 300K, using the magneto-optic Kerr effect. After a given deposition of Co in the thickness range 5ML<dCo<40ML, the M-H loop is observed to evolve continuously in time until the magnetic easy axis has switched 90° from the [001] to [1–10] direction. We attribute this behaviour to the reversal in sign of the effective in-plane uniaxial anisotropy constant, due to the adsorption of submonolayer quantities of a residual gas from the UHV environment. STM images reveal the growth of elongated Co island structures preferentially oriented along the [001] direction providing ‘step like’ edge sites for gas adsorption. We find the easy axis can be switched back to the [001] direction by depositing a submonolayer Cu overlayer, and that for relatively thick Co films (>15ML) the Cu overlayer can cause the magnetisation to take up intermediate angles. We analyse this behaviour using a simple model of the effective anisotropy energies.