NON-MAGNETOSTRICTIVE AMORPHOUS SOFT MAGNETIC THIN-FILM MATERIAL OF HIGH MAGNETIZATION

Magnetically uniaxial amorphous Co79Fe6.5B 14.5 films 1.5 μm in thickness were deposited by r.f. bias sputtering from a Co74Fe6B20 target onto glass and single crystal Si substrates. The saturation magnetostriction, λs, changed gradually from +0.6×10-6 to -0.4×10-6 when the d.c. bias voltage was increased from 0 to -120 V. In this bias voltage range 4πMs values from 11 up to 14 kG were measured. The influence of the Ar gas pressure on 4πMs and λs is weak. Coercivities of less than 0.05 Oe were obtained on Si substrates at bias voltages between -45 V and -90 V. The hard axis anisotropy field was decreased by hard axis field annealing at 240°C from 12 Oe to below 3 Oe and the initial permeability increased up to 3600. The amorphous state was not affected by the annealing. The electrical resistivity of the material was 90 μΩ cm and the magneto-resistivity ratio Δρ/ρ was 0.2%. The high values of 4πMs and of the permeability, zero λs, and low Hc, combined with a high electrical resistivity suggest the application of the material in thin film magnetic devices operating at high frequencies. As for permalloy films also Co79Fe6.5B14.5 films must be protected from corrosive influences.