Field dependence of FMR in ferrites and implications for microwave absorber design

Stephen George Appleton

doi:10.1117/12.210469

26 May 1995 Field dependence of FMR in ferrites and implications for microwave absorber design

Stephen George Appleton

Proceedings Volume 2448, Smart Structures and Materials 1995: Smart Electronics; (1995) https://doi.org/10.1117/12.210469
Event: Smart Structures and Materials '95, 1995, San Diego, CA, United States

Abstract

There are numerous potential uses for a microwave absorbent material whose absorption can be modified by an applied stimulus. This paper presents work to exploit the dependence of the microwave properties of ferrites on applied magnetic fields, and to develop such an absorbent material. Ferromagnetic resonance (FMR) is known to result in absorption of incident microwave energy at a characteristic frequency for any given ferrite. The FMR frequency is dependent on the anisotropy field H_an, which in turn can be modified by chemical doping. Therefore, ferrite RAMs can be produced to operate at required frequencies through judicious choice of the ferrite. Furthermore, if H_an is supplemented by an applied magnetic field H_app, the FMR frequency will be increased by an amount dependent on the strength of H_app and on the sense of anisotropy. The microwave permeability and permittivity spectra of a range of ferrites were measured as functions of H_app, using a vector network analyzer. These were used as input to a computer model for calculating absorber performance, and the effects of bias fields on a variety of absorber designs were predicted. A novel system was developed to apply large fields in test panels, for validating performance predictions.

Citation Download Citation

Stephen George Appleton "Field dependence of FMR in ferrites and implications for microwave absorber design", Proc. SPIE 2448, Smart Structures and Materials 1995: Smart Electronics, (26 May 1995); https://doi.org/10.1117/12.210469

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