title: Dipolar driven spontaneous self assembly of superparamagnetic Co nanoparticles into micrometric rice-grain like structures.
abstract: Superparamagnetic single crystal single domain Co nanoparticles of 6 nm in diameter evaporated onto highly pyrolytic oriented graphite spontaneously self-assemble into super structures with an elongated shape. These structures have been studied by optical and scanning electron microscopies, atomic and magnetic force microscopy, electron dispersive X-ray analysis, and SQUID magnetometry. We propose that the weak dipolar interactions between superparamagnetic dipoles of the cobalt nanoparticles are responsible for the formation of these structures when the dipolar magnetic interactions are strong enough to influence the general process of self-assembly dominated by van der Waals forces between neighboring nanoparticles and between nanoparticles and the substrate during evaporation of the solvent.
authors.affiliation: Institut Catala de Nanotecnologia, Campus UAB, 08193 Barcelona, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Varón
authors.forename: Luis
authors.initials: L
authors.lastname: Peña
authors.forename: Lluis
authors.initials: L
authors.lastname: Balcells
authors.forename: Vassil
authors.initials: V
authors.lastname: Skumryev
authors.forename: Benjamin
authors.initials: B
authors.lastname: Martinez
authors.forename: Victor
authors.initials: V
authors.lastname: Puntes