Ultrahigh frequency properties of amorphous Co-Fe-Zr-B thin films

Abstract

We have investigated ultrahigh frequency magnetic properties of amorphous Co-Fe-Zr-B alloy films deposited on glass substrates by dc magnetron sputtering. Microstructural characterization carried out on these films shows the amorphous nature of the films. The Co-Fe-Zr-B film with a thickness of /spl sim/2300 A exhibits excellent soft magnetic properties in the as-deposited condition, e.g., easy axis coercivity (H/sub c/) of /spl sim/1.5 Oe and 4 /spl pi/Ms of /spl sim/8.4 kG. The in-plane uniaxial anisotropy field (H/sub k/) is as high as /spl sim/28 Oe. This large anisotropy field significantly enhances the ferromagnetic resonance frequency (f/sub res/) to /spl sim/1.86 GHz. The relative permeability /spl mu/' of this film is shown to be /spl sim/200 and to stay nearly constant in the frequency range of 0.1 GHz-0.75 GHz. The full width at half maximum (/spl Delta/f) for the peak in the imaginary part of the permeability at resonance is /spl sim/0.35 GHz. It Is also found that the soft magnetic properties as well as the ultrahigh frequency properties of amorphous films have a strong dependence on film thickness. This is attributed to the change in the microstructure of films, which is closely related to the film growth conditions.