Enhanced high-frequency electromagnetic properties of FeCoB–SiO2/SiO2 multilayered granular films

Abstract A series of FeCoB–SiO 2 /SiO 2 multilayered granular films with various thickness were prepared by alternating co-sputtering FeCoB and SiO 2 targets and single-sputtering SiO 2 target. As-deposited films were annealed in a magnetic field at different temperature. The high-frequency magnetic and electrical transport properties were investigated. The films annealed above 250 °C show good soft magnetic properties and obvious uniaxial magnetic anisotropy. The resistivity ( ρ ), coercivity ( H ce ) decrease and complex permeability ( μ ˜ ), ferromagnetic resonance frequency ( f r ) increase with increasing annealing temperature and thickness. The desirable high ρ (∼5.92 mΩ cm), considerable frequency linewidth (Δ f ∼4.02 GHz) and high μ ˜ ( μ′ =120 at low frequency, μ max ″ = 80 ) were obtained for the 252 nm films annealed at 250 °C. The amorphous or nanograin phase and strong exchange coupling effect are responsible for the good high-frequency magnetic performance. The electrical transport properties show the films with high ρ and large μ ˜ are near the conductive percolation threshold. Moreover, the Δ f , damp coefficient ( α ) and Gilbert damping parameter ( G ) were discussed based on phenomenological Landau–Lifshitz–Gilbert equation.