Controlled Elaboration and Magnetic Properties of Submicrometric Cobalt Fibers

Abstract

Hexagonal close-packed cobalt fibers with a narrow size distribution and a submicrometric diameter have been successfully synthesized using a modified polyol process in the presence of an applied magnetic field of 500 Oe. The X-ray diffraction (XRD) and the scanning electron microscopy characterization showed that the structure, size, morphology, and dispersion of the as-prepared fibers were widely influenced by the synthesis parameters (hydrolysis ratio, reactant concentration, reaction temperature, and time). The selected area electron diffraction pattern revealed that the as-prepared fibers are polycrystalline. Magnetic measurements on cobalt samples showed enhancement of their ferromagnetic properties, which may be attributed to their anisotropic shape. Irreversibility in the zero-field-cooling and field-cooling measurements was observed and could be interpreted in terms of the unblocking of magnetization of small-domain particles and domain wall depinning of larger multidomain particles.