The Kerr intensity versus the Ag thickness for Ag grown on the top of Co/Ir(111) exhibits an oscillating behavior with a period around one monolayer which should be due to the morphological change related electronic structure differences of the Ag layer. From systematical investigations of Ag/Co/Ir(111) films with the Co layer thinner than 4 monolayers at temperatures below 900 K, a magnetic phase diagram has been established. As the annealing temperature increases for Ag/Co/Ir(111) films, enhancements of the coercive force occur in both the polar and longitudinal configurations due to the intermixing of Ag and Co at the interface and the formation of Co-Ir alloy. The disappearance of ferromagnetismis mainly attributed to the reduced atomic percent of cobalt in Co-Ir alloy, the lowered Curie temperature by a reduction of the thickness of magnetic layers, and the intermixing of Ag and Co at the Ag/Co interface. (C) 2013 Elsevier B. V. All rights reserved.