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 Å) 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.