The dissertation presents research results from integrated studies of process, structure and magnetic properties of plasma-sprayed ferrite-metal composites. These magnetic composites are considered as the core materials for miniaturized high frequency planar inductors, thick film magnetoresistive sensors and potentially as magnetostrictive sensors. Offering the advantages of low substrate temperature during processing, high throughput production capability, cost efficiency and minimizing the interfacial reaction between the ferrite and metal phases, plasma spraying can be considered as a promising route for fabricating magnetic composites with industrial applications. A multitude of experimental techniques, including phase analysis, microstructure observation, magnetic property and electrical property measurements and numerical modeling have been applied for this investigation.

A number of fundamental attributes in terms of process-microstructure-property relationships have been investigated by a systematic processing approach through the frame work of process maps. Such studies can provide insight into process control and optimization.

Three types of magnetic composites have been fabricated using plasma spraying. Rocksalt structured monoxides form in the as-sprayed coatings due to deoxidation of ferrite as well as the oxidation of metallic particles. Random cation distribution and the presence of monoxides and microstructural defects, degrade the magnetic and electrical properties of the composites. Low temperature air annealing can improve these properties by means of forming insulating trivalent oxides (Hematite) and ordering the cations. Functional properties such as magnetoresistance and magnetostriction of comparable value to bulk materials can be obtained after annealing.

A salient finding is the transition form a giant magnetoresistance (GMR) to anisotropic magnetoresistance (AMR) at the percolation threshold which has been reported for the first time in magnetic composites. Thermally sprayed composites coatings are found to have a much smaller percolation threshold due to the anisotropy of splats. Using the effective medium approximation, the relationship between the percolation threshold and aspect ratio has been derived. The experimental results are in good agreement with simulation results. This is the first time that the percolation phenomenon in thermally sprayed composites has been studied quantitatively and compared with theory.