Spectra of impedance and dielectric loss tangent in the frequency range 10 Hz–10 MHz and in the temperature range 120–420 K and magnetic structure of composite films (CoFeB+SiO$_2$)

In this work, temperature and frequency dependences of real and imaginary parts of impedance, relative permittivity and dielectric loss tangent of composite films (CoFeB + SiO$_2$) were obtained by impedance spectroscopy. The composite films with the metal alloy concentrations $x$ = 0.46 – 0.92 were on a polyethylene terephthalate substrate. The studies were carried out in the frequency range 10 Hz –10 MHz and in the temperature range 120–460 K. Images of surface topography and magnetic phase contrast of the composite films with the concentrations were obtained using an atomic force microscope. Maximum loss tangent was observed at frequencies of 70–120 kHz throughout the entire temperature range for the films with the concentrations from 0.62 to 0.72, for which a stripe magnetic structure was observed. The real part of the impedance of the composite films with the concentrations of 0.62 – 0.92 decreases exponentially with increasing the frequency from 10 Hz to 10 MHz throughout the entire temperature range studied.