Adsorbate influence on the coercive field of ultrathin Co/Cu{1Â 1Â 0}

We report on experimental coercive field measurements for ultrathin films of Co on Cu{1 1 0}, revealing a complex dependence upon the surface coverage of oxygen and hydrogen adatoms. With reference to first-principles calculations, we rationalise this behaviour in terms of initial reaction with surface contaminants and/or adsorption at defects, followed by (in the case of oxygen) subsequent surface ordering and eventual formation of surface oxide.