Interplay between interfacial and structural properties on the magnetism of self-organized core-shell Co/Pt supported nanodots

Abstract

We have studied the influence of Pt capping on the magnetic properties of self-organized Co nanodots by means of complementary structural and magnetic investigation techniques. The growth of monodisperse 5 nm diameter Co dots on a Au(111) surface and its progressive coverage by Pt were performed under ultrahigh vacuum conditions and imaged by scanning tunneling microscopy, revealing a weak mixing at room temperature. The Co/Pt core-shell structure was studied both by molecular-dynamics simulations and surface extended x-ray-absorption fine structure, showing a global dilatation of the Co core. Both magnetic moments and hysteresis cycles at various temperatures were measured using x-ray magnetic circular dichroism, revealing a slight increase of the magnetic moments and the out-of-plane magnetic anisotropy after Pt capping. Moreover, the variation of magnetic anisotropy as a function of capping was followed in situ by the magneto-optical Kerr effect. Our investigations demonstrate that interfacial hybridization between Co and Pt is dominant over magnetoelastic contribution in this system.