Processing and application of magnetoelastic thin films in high-frequency devices

Magnetoelastic thin films and multilayers were optimized to exhibit a high inverse magnetostrictive effect and a high ferromagnetic resonance frequency. FeCo/CoB and FeCoBSi films were used in two promising applications, a resonant LC circuit and a transmission line. In both cases the basic structure is a strip line with magnetic sandwich layers, which increase the inductance. In the resonant circuit design, a magnetic field or stress applied to the device changes the permeability of the magnetic layers and therefore the inductance and the resonance frequency of the device. Resonance frequencies of about 500 MHz with quality factors of up to 8 could be achieved. Such LC circuits can be used as remote interrogated stress or torque sensors. The second design is a transmission-line device, which shows a large wavelength shortening effect and can be used as a band filter in GHz applications. (C) 2003 Elsevier Science B.V. All rights reserved.