A Possibility of Magnetic Field Biasing Tunable Inductive Device Using a Hard Magnetic Film Magnetized by Pulsed-Magnetic Field

In this paper, the authors have proposed a possibility of a magnetic field biasing tunable inductive device. To confirm a new scheme, a tunable coplanar waveguide (CPW) resonator with a combination of soft magnetic thin film and hard magnetic film has been fabricated and evaluated. The magnetic pole of hard magnetic film can be controlled by magnetization using a pulsed magnetic field. A bias magnetic field is applied in the soft magnetic film from the magnetic pole of the hard magnet film. Consequently, permeability of the soft magnetic film can be controlled by changing amplitude of the pulsed magnetic field in the magnetizing for the hard magnetic film. A 20 mm long coplanar wave guide resonator has been fabricated using FeSiO/SiO₂ granular multilayer film and FeCoSm amorphous hard magnetic film. From the experimental results, in case of using 0.2 μm thick soft granular film, by changing amplitude of the 1 ms width current-pulse for magnetizing pulsed magnetic field for hard magnetic film, the maximum inductance change was up to 18%, and maximum change of the resonant frequency was 9.6%. The control energy for one time tuning was small enough (5.4 μWh ).