Synthesis And Magnetic Properties Of Nanostructured Ferromagnetic Metal

Magnetic properties of nanopaticles,especially the dependence of magnetic properties on the particle size and shape have been attracted more interests for a long time. The shape and surface play more important when the size of ferromagnet becomes smaller thus its magnetic properties can be controlled by modification of their shape and size. In this thesis, we synthesized nanostructures of nickel and cobalt with different shape and size by self-assembly methods and studied their properties by morphology observation, structure analysis and magnetic measurements. The major results are summariaed as follows:Different shaped Ni particles are synthesized including spherical nanopaticles with diameter of 100 nm, acicular nickel nanoparticles with length of 100nm, width of 10-20nm and thickness of 10nm, flake-shaped Ni particles with diameter of 100 nm and thickness of 20 nm, and hollow nickel particles with inner and outer diameter of 100 nm and 300 nm. one-dimensional structures of Ni with different aspect ratio have been obtained by applied magnetic field during reduction process .A systematical investigations on morphology, structure and magnetic properties of nickel particles with different shape have been taken by using SEM, TEM, XRD and VSM. Dependence of magnetic properties on the particle size and shape has been discussed in this article. Micromagnetic simulation have also been made on different shape of nickel nanostructures, which can qualitatively explain the experimental results.Different shaped Co particles are synthesized including clusters of Co single crystal with diameter of 1.5 micrometer, amorphous cobalt nanoparticles with diameter less than 100nm. The treatments of annealing and coating have been applied to improve the magnetic properties of amorphous cobalt nanoparticles. One-dimension structures of cobalt with defferent aspect ratio have also been obtained by applied magnetic field.Morphology, structure and magnetic properties of Co have been studied by using SEM, TEM, XRD and VSM. Experimental results indicate that surface coating as well as particle size and shape can also influence magnetic properties. Micromagnetic simulations on Co nanostructures approximately agree with the experimental results.