Impedance model of metal-dielectric nanocomposites produced by ion-beam sputtering in vacuum conditions and its experimental verification for thin films of (FeCoZr)x(PZT)(100−x)

Abstract

The paper presents results of testing electric properties (resistance, capacity and phase angle in an equivalent parallel circuit) of ferromagnetic alloy-dielectric nanocomposites (FeCoZr)x(PZT)(100−x) produced by ion-beam sputtering in vacuum conditions. The measurements have been performed using alternating current within the frequency range of 50 Hz–1 MHz for measuring temperatures ranging from 77 K to 373 K. In nanocomposites (CoFeZr)x(PZT)(100−x), produced by ion beam sputtering using a beam of combined argon and oxygen ions, for x approaching the percolation threshold, frequency dependences of the phase angle φ that resemble those occurring in RLC parallel circuits have been observed. In the low frequency area, the phase angle of 90° ≤ φ < 0° occurs. It corresponds to the capacitive type of conduction. In the high frequency area, the inductive type of conduction with 0° ≤ φ ≤ 90° occurs. At the resonance frequency f0, characterized by the phase angle of φ = 0°, the capacity value reaches its strong local minimum. A theoretical basis for a model of the AC hopping conduction for metal-dielectric nanocomposites has been developed and on that basis frequency dependences of the phase angle, resistance and capacitive current density components have been analyzed. The obtained theoretical and experimental results have been compared.