In order to increase Q-factor of RF magnetic thin film inductor integrated in Chip-size-package RF-ICs, two schemes have been investigated experimentally. For suppressing the in-plane eddy current of the magnetic thin film, a slit-patterned structure was introduced, and it was found that the slit-patterned magnetic thin film is very effective for increasing Q-factor. On the other hand, for suppressing ac copper loss, a multi-line-conductor spiral coil was introduced, and it was found that the multi-line coil is effective for improving decrease of inductance at high frequencies. By introducing the two schemes, a maximum Q-factor of 18 at 1.5 GHz was obtained in a spiral inductor with a bottom slit-patterned CoFeSiO/SiO 2 granular multilayer film and triple-line-conductor spiral coil.
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/SiO 2 granular multilayer film and FeCoSm amorphous hard magnetic film. From the experimental results, in case of using 0.2 m thick soft granular film, by changing amplitude of the 1 ms width currentpulse 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 Wh).Index Terms-Tunable inductive device, cell phone, hard magnetic film, soft magnetic film, pulsed-current magnetization method.
We have measured the local differential conductance spectra (dI/dV -V) of an itinerant ferromagnet composed of polycrystalline SrRuO 3 using the mechanically controllable break junction technique. Below the material's Curie temperature (T C = 160 K), characteristic peak or dip conductance spectra are observed.The characteristic energy scale is comparable to the exchange spin splitting energy that is based on ferromagnetic band calculations. Both the peak and dip spectral shapes are explained based on the itinerant ferromagnetic characteristics of SrRuO 3 in terms of spin-dependent transmission, which is similar to the giant magnetoresistance mechanism.
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