A study on the interislands interaction in granular Fe(110) thin films grown on c-sapphire as a function of the islands size and the capping layer induced magnetization is presented. Islands size (ranging from 10 to 50 nm in diameter) and physical contact between them can be monitored with the deposition time. While Al and MgO cappings do not modify the magnetic hysteresis loop of free islands surface, Pd and Pt give rise to a superparamagnetic-ferromagnetic transition in structures formed by small islands and a stronger interisland coupling in those formed by larger ferromagnetic islands. This improvement in the exchange interactions between islands is due to the induced magnetization of Pt and Pd localized at the interfaces between Pt-Fe(Pd-Fe) as evidenced by polar Kerr spectroscopy measurements and simulations.

This work has been partially financed by the Spanish Commission of Science and Technology, Comunidad Autónoma de Madrid, and the Spanish Ministerio de Ciencia y Tecnología. Y.H. acknowledges the Consejo Superior de Investigaciones Científicas (CSIC) and Ramón y Cajal program for financial support.

Peer reviewed