http://www2.physics.colostate.edu/groups/WuGroup/publications/MMM_2009_Recent%20advances%20in%20processing%20and%20applications%20of%20microwave%20ferrites.pdf

Recent advances in processing and applications of microwave ferrites

Microwave ferrites are ubiquitous in systems that send, receive, and manipulate electromagnetic signals across very high frequency to quasi-optical frequency bands. In this paper, modern microwave ferrites are reviewed including spinel, garnet, and hexaferrite systems as thin and thick films, powders and compacts, and metamaterials. Their fundamental properties and utility are examined in the context of high frequency applications ranging from the VHF to millimeter-wave bands. Perspective and outlook of advances in theory, processing, and devices occurring in the science and engineering communities since the year 2000 are presented and discussed.

Modern Microwave Ferrites

Solution deposition of thin solid compound films by a successive ionic-layer adsorption and reaction process

Many techniques for the synthesis of ceramic thin films from aqueous solutions at low temperatures (25–100°C) have been reported. This paper reviews non-electrochemical, non-hydrothermal, low-temperature aqueous deposition routes, with an emphasis on oxide materials for electronic applications. Originally used for sulfide and selenide thin films, such techniques have also been applied to oxides since the 1970's. Films of single oxides (e.g., transition metal oxides, In2O3, SiO2, SnO2) and multicomponent films (doped ZnO, Cd2SnO4, ZrTiO4, ZrO2-Y2O3, Li-Co-O spinel, ferrites, perovskites) have been produced. The maximum thicknesses of the films obtained have ranged from 100 to 1000 nm, and deposition rates have ranged from 2 to 20,000 nm/h. Compared to vapor-deposition techniques, liquid-deposition routes offer lower capital equipment costs, lower processing temperatures, and flexibility in the choice of substrates with respect to topography and thermal stability. Compared to sol-gel techniques, the routes reviewed here offer lower processing temperatures, lower shrinkage, and (being based on aqueous precursors) lower costs and the potential for reduced environmental impact. This review emphasizes the influence of solution chemistry and process design on the microstructures and growth rates of the films. The current understanding of the mechanisms of film formation is presented, and the advantages and limitations of these techniques are discussed.

Review: Deposition of ceramic thin films at low temperatures from aqueous solutions

Permanent magnet films for applications in microelectromechanical systems

This paper describes the principle and performance of a new technique which facilitates the formation of crystalline spinel film at low temperature (T<80 °C) without a heat treatment. For a substrate, not only a metal but also oxides and organic compounds can be used. Various transition metals (M=Ni, Co, Mn, Cu, Zn, etc.) are incorporated into the spinel. Hydrolyzed metal ions FeOH+ and MOH(n−1)+ in an aqueous solution (pH=6∼11,T=40∼80 °C) are adsorbed on a substrate surface which react into spinel film associated with anodic or air oxidation of the FeOH+ ion. We have plated Fe3O4 and CoFe2O4 films on a substrate of Cu, polyethylene terephthalate, and stainless steel. They are polycrystalline with no preferred orientation, and exhibit no magnetic anisotropy. The polar Kerr rotation of these films has been measured.

Yutaka Tamaura

Papers

Ferrite plating in aqueous solution: New technique for preparing magnetic thin film