High-resistive (CoFeB)-(SiO2) soft magnetic amorphous film for micro-coresin a few MHz range

Highly resistive (CoFeB)-(SiO2) amorphous films were deposited on glass sub strates and polyimide sheets by synchronous dual-rf magnetron sputtering, S iO2 volume fraction dependence of magnetic properties and resistivity was i nvestigated, The as-deposited films for SiO2 volume fraction nu=20 vol.% ha d low coercivities of H-c=0.2-0.3 Oe, together with high resistivities of 1 500-2200 mu Omega cm, The film exhibited an anisotropy held 40 Oe, a relati ve permeability of 200 and a saturation magnetization of 7.3 kG, The core l oss of the films was 1-1.5 J/m(3) at I MHz for maximum flux density B-m=0.1 T. The loss was found to be as low as those of Co-based ultra-thin ribbons [3]. The films are useful as thin film cores in the micromagnetic elements which work in the MHz range.