Ag-related alloy formation and magnetic phases for Ag/Co/Ir(111) ultrathin films

• An oscillating behavior occurs due to the morphological change for Ag on Co/Ir(111).
• A magnetic phase diagram has been established for Ag/Co/Ir(111).
• Some Ag atoms intermix with the underlying Co layer at high temperatures.
• Polar coercive force is enhanced due to the compositional change.

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 ferromagnetism is 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.