SBIR-STTR Award

Ferrimagnetic oxides with hexagonal crystal structure are characterized primarily by their foliate (leaf-like or platelet) structure and high anisotropy fields. These highly anisotropic compounds can be prepared as a composite composed of single domain grains possessing a spectrum of controlled values of anisotropy fields and attendant preferred direction of magnetization. These hexagoal single domain grains with predictable and controlled properties including the "built in" effective magnetic field (up to 50 kilo-oersteds) in both uniaxial and planar structures, will thus provide a composite structure in which the complex permeability and dielectric properties of the composite can be optimized for broadband microwave absorptive characteristics through resonance interactions. Absorptive characteristics will be controlled through ferromagnetic resonance (domain rotation) interactions with the randomly oriented magnetic moments, biased grain by "built-in" internal anisotropy fields and through conductive processes associated with optimization and control of the complex dielectric properties.

Ferrimagnetic oxides possess permeability and permittivity properties which can be utilized effectively for microwave absorption. Highly anisotropic hexagonal ferrites compounds, as well as those of the spinel ferrite family, can be prepared and used as pigment composed of single domain grains possessing a spectrum of controlled values of anisotropy field and attendent preferred direction of magnetization. This pigment used as a composite part of paints and coatings can be utilized to optimize the complex permeability and dielectric properties to achieve broadband microwave absorptive characteristics. Absorptive characteristics will be controlled through ferromagnetic resonance interactions with randomly oriented magnetic moments biased grain to grain by "built-in" internal anisotropy fields and through conductive processes associated with optimization and control of the complex dielectric properties.