Growth of ferromagnetic particles from cation reduction by borohydride ions

Abstract

An experimental and theoretical study on the formation of ferromagnetic particles from cation reduction by borohydride is reported. The effects of various parameters on primary particle size, composition, saturation magnetization, and chain formation have been studied. These parameters include the metallic cation and its concentration, the anion concentration, the reaction temperature, and the use of additives in the reaction. A relationship has been demonstrated between the fractal dimension of aggregates and their saturation magnetization. In basic media, primary particle formation has been shown to occur by two different mechanisms depending on the metallic cation concentration. A model has been developed which gives results in agreement with experimental observations on the formation of primary particles at higher metallic cation concentrations in basic media; the model indicates that primary particle growth occurs primarily by condensation of atoms on clusters and that collisions between clusters are probably suppressed by electrical double-layer forces.