The high‐resistive soft magnetic amorphous films consisting of cobalt, iron, boron, silicon, and oxygen, utilized for video head devices

A new type of high‐resistive soft magnetic amorphous film possessing superior properties such as high resistivity (ρ), high‐saturation induction (Bs), and high permeability (μ) in the high‐frequency range prepared by cosputtering Co0.40Fe0.40B0.20‐SiO2 was obtained. These films which have Bs higher than 8 kG in the range less than ∼55% of Si‐O volume fraction, consist of a two‐phase structure of amorphous magnetic metal particles (∼50 A) scattered in the amorphous nonmagnetic Si‐O region. ρ increases exponentially with the increase of Si‐O volume, with diminishing eddy current loss in the very high‐frequency range. Some of these films (Bs∼12 kG, Hc∼0.3 Oe, ρ∼500 μΩ cm), in fact, have a superior permeability compared with sputtered sendust films and regular amorphous films used as high‐density recording head cores in the high‐frequency range over 10 MHz.