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The study presents frequency dependences of real part of admittanceZ′(f) and phase shift angleθ(T,f)innanogranularfilms containing CoFeZr nanoparticles with“core-shell”structure embedded into SiO2matrix. The3μm thicknesses (Co41Fe49Zr10)x(SiO2)100−xfilms with 20≤x≤80 at.% were deposited in vacuum chamberevacuated either with pure Ar (Set 1 samples) or Ar + O2gas mixture (Set 2) using ion-beam sputteringtechnique. After characterization by X-Ray diffraction, Mössbauer spectroscopy, scanning electron microscopyand magnetization studies, thefilms both of Set 1 and Set 2 samples were subjected by admittance measurementsat 300 K in the frequency range of 0.1–1000 kHz. Mössbauer spectroscopy have shown that oxidized CoFeZrnanoparticles in Set 2 samples contain semiconducting iron-based oxides with Fe3+charge states of iron ions.The observedZ′(f) andθ(f) dependencies for the Set 2films below thexchave shown dielectric regime of carriertransport. They also exhibited that at weak AC electricfields inductive-like contribution to reactive part ofadmittance (with positiveθvalues) prevails over the capacitive onef> 10 kHz. This effect of the so-called“negative capacitance”was explained by the delay of current, formed by electrons hopping between nano-particles, relative to applied bias voltage. This delay is forced by formation of dipoles of charged FeCoZr na-noparticles with native Fe-based oxide“shells”around them that results in the increase of mean life time ofhopping electrons on nanoparticles with“core-shell”structure.
