MAGNETIC CORES USABLE IN GHz RANGE MADE BY COMPRESSING NiFe MICROSPHERES ENCAPSULATED WITH NiZn FERRITE BY WET PROCESS

摘要

This paper presents a novel type of magnetic cores usable up to GHz frequencies. Soft magnetic metal microspheres were encapsulated by ferrite films by the wet process, which were compressed to form the composite magnetic cores. In general, metals have very high (exceeding several GHz) natural ferromagnetic resonance frequencies (criteria for usable frequency), which are, however, buried by eddy current loss due to the high metallic conductivity. In our novel composite cores the insulating ferrite coat suppress the eddy current. This facilitates fabrication of magnetic cores operated in GHz range, which are strongly demanded at present to ensure stable operation of most advanced personal computers and cellular phones driven at above 2 GHz.