New applications of high resistivity magnetic films, such as Fe–Hf–O and Co–Fe–Hf–O as thin film inductors and flux gate magnetic sensors, were investigated. These soft magnetic films with nanocrystalline structure and high resistivity were deposited on glass substrate by using the oxygen reactive sputtering method. Planar sandwich thin film inductors developed by using Fe–Hf–O or Co–Fe–Hf–O films had a higher quality factor than that of an amorphous Co–Ta–Hf film inductor. The dc–dc converter using the Fe(Co–Fe)–Hf–O film inductor had higher conversion efficiency. These high resistivity magnetic films were also applied to a flux gate magnetic sensor operated at high frequencies over 1 MHz. Both high frequency excitation and high permeability (owing to the low eddy current loss) enabled us to increase the sensitivity, e.g., 39 mV/Oe/turn at 5 MHz when using a 3 μm thick Fe–Hf–O film (12×6 mm2 area).
High resistivity magnetic films, such as reactive sputtered and Co-Fe-Hf-0, were applied to multilayered micro reactors for high frequency operation dc-dc converters. For a comparison, an amorphous Co-Ta-Hf film with good soft magnetic properties was also investigated. The micro reactor had the highest quality factor(the lowest loss) when using Cc-Fe-Hf-0 f i l m with the highest resistivity. In SMHz operation of dc-dc converters using these micro reactors, the ncy was obtained when
~.~~0 D~~~~Recently, the miniaturization of cellular phones and personal computers has been in e key t e c~~o~~~~e s for n is the down-sizing of magnetic verters using thin s in the eddy current loss in the high ~e~u e~c y range are now required for further ( f, Zr, rare earth) [4][5] and f-0161 soft magnetic films exhibit high resistivity as well as high saturation constant up to 1 described.
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