| In this paper, from the experimental aspect in which magnetic nanowire and nanoparticle arrays are synthesized and investigated and the simulation aspect in which micromagnetic models of the arrays of nanomagnets are established and analyzed, the magnetic characteristics of the arrays of magnetic nano-materials are researched. Our main conclusions are listed below.1. The magnetic nanowire arrays have a strong magnetic anisotropy which has an easy direction perpendicular to the array plane. The strength of this anisotropy can be changed by experimental parameters, which makes it reasonable that the anisotropy originates mainly from the shape anisotropy of individual nanowires. The results of the remanent magnetization measurements of Fe nanowire arrays indicate the nucleation and wall-moving mechanism in the magnetization process of Fe nanowires; and magnetic interactions in the array are those between the magnetic particles within individual nanowires and different nanowires, the latter are thought necessary when researching the magnetization mechanism of the nanomagnets array.2. The relation between coercivity and temperature is found in the magnetic nanoparticle arrays. When functionalize the relation and compare it with that of the classical Stoner-Wohlfarth particle system, we conclude there is a large strength of the magnetic interactions between the nanoparticles.3. By using micromagnetic techniques, the analytical expressions of the magnetic dipolar interactions between nanoparticles and a phase diagram of the ground states in 2D arrays of magnetic nanoparticles are obtained. Based on our reversal mechanism of the particle array, all possible hysteresis loops of the system and some analytical expressions of the coercivities or saturation fields are achieved. These results show that the shape ratio of the particle and the particle density of the array are main factors affecting the magnetism in 2D arrays of magnetic nanoparticles. A new numerical simulation method is also applied to study the hysteresis loops of the system. Some more reasonable results are obtained comparing with the experimental data and the limitation of this method is discussed too. 4. The self-assembly of Fe-B amorphous alloy nanoparticles is synthesized within a throughout porous AAO template for the first time. These nanoparticles have very small controllable diameters and relatively narrow distribution of their sizes. Most of the particles are in superparamagnetic states and the self-assembly is found to have a weak magnetic anisotropy. This template method to prepare ultrafine particles is thought has important potential applications and can give some distinctive properties. |
