Thin-film permanent magnet requirements for magnetic devices in MMIC (invited) (abstract)

Abstract

Sputtered permanent-magnet thin films1 may offer an attractive alternative to bulk permanent magnets for biasing microwave magnetic devices. Such films could significantly reduce the size, weight, and cost of these devices in geometries compatible with MMIC. A film of uniform thickness magnetized normal to its plane would only generate strong external fields near its edges, however, and so would not be effective for bias purposes. Thus uniform films with in-plane remnant moments are of primary interest. (Normally magnetized films with nonuniform thicknesses may be useful in cladding layers for flux confinement, but are not considered here.) Although field inhomogeneities inherent in the use of thin-film permanent magnets may be a problem for some resonant devices, below-resonance devices should be tolerant of inhomogeneities so long as the net internal field in the ferrite is small compared to the saturation magnetization, and ω>γ4πM. Examples are discussed suggesting how such films could be used to bias phase shifters, circulators, and magnetostatic wave devices.