High-frequency magnetic permeability of single- and multilayered (Co$_{41}$Fe$_{39}$B$_{20}$)$_{x}$(SiO$_{2}$)$_{100-x}$ nanocomposites

Thin film single-layered (Co$_{41}$Fe$_{39}$B$_{20}$)$_{x}$(SiO$_{2}$)$_{100-x}$ nanocomposites at $x$ = 30–80 at % and multilayered nanocomposites composed of 176 pairs of [(Co$_{41}$Fe$_{39}$B$_{20}$)$_{60}$ (SiO$_{2}$)$_{40}$]/[(Co$_{41} $Fe$_{39}$B$_{20}$)$_{60}$(SiO$_{2}$)$_{40}$+O$_{2}$] have been prepared via ion-beam sputtering of the complex target. The concentration dependences of the magnetic permeability of single-layered films at a frequency of 50 MHz are characterized by maximum losses near $x$ = 60 at %, whereas the percolation threshold with respect to the electric conductivity is $x$ = 50 at %. The high-frequency magnetic permeability of films has been measured by the resonator method in the frequency range of 0.1–10 GHz. As is shown, while the single-layer film passes to the multilayered structure, the ferromagnetic resonance frequency shifts from 1.5 to 2.5 GHz, and the imaginary part of the magnetic permeability attains 200 that is presumably due to the inhibition of the perpendicular magnetic anisotropy component.