Soft magnetic and high-frequency properties of FeCoB-SiO2 granular films deposited on flexible substrates

A series of FeCoB-SiO2 granular films were deposited on Kapton flexible substrates by magnetron co-sputtering technique at room temperature. All films are amorphous with granular morphology. The coercivity in the easy axis (Hce) and the resistivity (ρ) decrease with the decrease of the Ar pressure, but they decrease with the increase of the film thickness. The granular films deposited at low Ar pressure exhibit obvious in-plane uniaxial magnetic anisotropy. Excellent soft magnetic properties with the Hce as low as 1.57 Oe was obtained in the 500 nm films deposited at 0.3 Pa. In addition, high ρ (∼3.5 mΩ cm), relatively high complex permeability (μ′ = 152.8 at low frequency and μmax″=221.2) and ferromagnetic resonance frequency (fr ∼ 3.61 GHz) were simultaneously obtained.