Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/8642
Title: Synthesis, structural order and magnetic behavior of self-assembled epsilon-Co nanocrystal arrays
Author: Puntes, Víctor
Krishnan, K. M.
Keywords: Cobalt
Col·loides
Propietats magnètiques
Materials nanoestructurats
Cobalt
Colloids
Magnetic properties
Nanostructured materials
Self-organizing systems
Issue Date: 2001
Publisher: IEEE
Abstract: The synthesis of magnetic nanoparticles with monodispere size distributions, their self assembly into ordered arrays and their magnetic behavior as a function of structural order (ferrofluids and 2D assemblies) are presented. Magnetic colloids of monodispersed, passivated, cobalt nanocrystals were produced by the rapid pyrolysis of cobalt carbonyl in solution. The size, size distribution (std. dev.< 5%) and the shape of the nanocrystals were controlled by varying the surfactant, its concentration, the reaction rate and the reaction temperature. The Co particles are defect-free single crystals with a complex cubic structure related to the beta phase of manganese (epsilon-Co). In the 2D assembly, a collective behavior was observed in the low-field susceptibility measurements where the magnetization of the zero field cooled process increases steadily and the magnetization of the field cooling process is independent the temperature. This was different from the observed behavior in a sample comprised of disordered interacting particles. A strong paramagnetic contribution appears at very low temperatures where the magnetization increases drastically after field cooling the sample. This has been attributed to the Co surfactant-particle interface since no magnetic atomic impurities are present in these samples.
Note: Reproducció del document publicat a http://dx.doi.org/10.1109/20.951126
It is part of: IEEE Transactions on Magnetics, 2001, vol. 37, núm. 4 (Part 1), p. 2210-2212.
URI: http://hdl.handle.net/2445/8642
ISSN: 0018-9464
Appears in Collections:Articles publicats en revistes (Física de la Matèria Condensada)

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