Properties of thin magnetic films for microwave applications

The microwave properties of thin magnetic films are described and are compared with ferromagnetic insulators. Consequences of two processes which give rise to some special properties are examined, namely the initial permeability and the gyromagmetic permeability. The specific topics include a comparison of the frequency response of ferrites and films; electromagnetic wave transmission through thin magnetic films, with particular regard to controlling the power flow by changes in permeability; discussion of the limitation imposed by the skin depth to obtain an adequate number of effective spins; potential applications of the initial permeability at microwave frequencies; and, finally, a description of a scheme which, in principle, represents a spin parametric amplifier.