Correlation between magnetic properties of layered ferromagnetic/dielectric material and tunable microwave device applications

Layered dielectric / ferromagnetic materials are extensively explored for microwave applications. Indeed, these materials combine the large saturation magnetization of ferromagnetic material with the low loss of dielectrics. Here, our aim was to integrate a layered ferromagnetic composite in a microwave propagation structure since the main advantage of such a material is the large impedance for one polarization. Thus, in order to predict the transmission response of the device, we carried out an electromagnetic analysis to determine how the field pattern of a microstrip line and the microwave-induced demagnetizing fields disturb the material behavior. We also explored the use of the propagation structure in two dc magnetic field-dependent devices: a tunable band stop filter and a magnetic switch. The stop-band function presented a large tunability of more than 50% with a minimal insertion loss of 3 dB when 250 Oe field was applied. Moreover, a magnetic switch using a dc field perpendicular to the easy axis of the ferromagnetic material was manufactured.