The authors have fabricated the polycrystalline Li-Zn-Cu ferrite as a new temperature sensitive ferrite. The Li-Zn-Cu ferrite had high-frequency permeability profile and high electrical resistivity as well as the Ni-Zn-Cu ferrite for multilayered surface-mounting device such as a high-frequency chip inductor and filter. Since the new Li-Zn-Cu ferrite had both excellent high-frequency magnetic property and temperature sensitivity, it will be suitable for miniaturization of high-frequency inductive temperature sensing device. In this study, the relationship between grain size and the temperature-dependent magnetic properties of polycrystalline Li-Zn-Cu ferrite has been investigated. Three kinds of the Li-Zn-Cu ferrites sintered with Bi 2 O 3 at different temperature were synthesized, and their temperature characteristics were evaluated. The most important result obtained is as follows: as the sintering temperature rose the coarse grain increased without changing bulk density, the permeability and its temperature dependence can be enhanced by grain growth due to higher sintering temperature. Therefore, the temperature dependent permeability of the Li-Zn-Cu ferrite can be controlled by grain size only without a change of the chemical composition.

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This paper discusses near field, conduction and crosstalk noise suppression of magnetic films with uniaxial anisotropy on transmission lines for a film-type noise suppressor in the GHz frequency range. The electromagnetic noise suppressions of magnetic films with different permeability and resistivity were measured and simulated with simple microstrip lines. The experimental and simulated results of Co-Zr-Nb and CoPd-CaF2 films agreed with each other. The results indicate that the higher permeability leads to a better near field shielding, and in the frequency range of 2–7 GHz, a higher conduction noise suppression. It also suggests that the higher resistivity results in a better crosstalk suppression in the frequency range below 2 GHz. These results can support the design guidelines of the magnetic film-type noise suppressor used in the next generation IC chip.

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