Capping layer effects in the structure and composition of Co nanoparticle ultrathin films

摘要

In this work, we present the correlation of the magnetic and structural properties of Co nanoparticles deposited by sputtering on Si_3N_4 substrates at different temperatures, and covered with different capping layers, two insulators, A1N and MgO, and a metal, Pt. High-resolution transmission electron microscopy shows the formation of CoPt_3 and Co_2N, for the Pt and A1N capping layers, respectively, giving to a significant change of the magnetic behavior. When using a cap of MgO, energy-filtered transmission electron microscopy shows an oxidized shell covering the Co nanoparticles with thickness decreasing as the deposition temperature increases, explaining the changes in the magnetic response induced by the MgO capping layer.