Nanoparticles and ultrathin films can show, in many cases, distinct properties from those presented in their bulk phases. These materials play a fundamental rule in the modern materials science and technology. The peculiar electronic, chemical, optical and magnetic properties in nanoparticules are mainly ruled by their size (size effect). In a similar way, ultrathin films grown on substrates with selected crystalline symmetry might have their electronic, structural and magnetic properties strongly influenced by the atomic arrangement of the substrate surfaces, as well as, by the film thickness and thermodynamic condition of growth. Among the anomalous effect displayed by nanoparticles and ultrathin films, there is the recent observation of ferromagnetism in noble metals and transition metals which do not show any ferromagnetic behavior in their bulk phases. This unexpected behavior has been recently predicted by using first principle theory and verified in some few experimental works. In this project, the student will characterize the magnetism in gold and palladium nanoparticle samples (already chemically synthesized), correlating these results with the structural and electronic properties of the nanoparticles. It will be done by a multi-technique approach, using X-ray Circular Magnetic Dichroism (XMCD), Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS). The main goal will be confirm the existence (or not existence) of ferromagnetism in these nanoparticles addressing the origin of magnetism. In a second step, ultrathin films of Pd (an enhanced Paulis paramagnetic metal) will be grown on Ru(0001), C(0001) and Nb(001) by using MBE. The idea is induce ferromagnetism in those films purely due structural and electronic mechanism. These samples will also be magnetically (XMCD), electronically (XPS and XANES) and structurally (EXAFS) characterized.
News published in Agência FAPESP Newsletter about the scholarship: