The goal of present paper was to investigate the influence of phase composition on DC and AC conductance of film composites containing CoFeZr nanoparticles (6 to 10 nm dimensions) in aluminium oxide matrix for atomic concentrations of metallic fraction x = 30-65 %.
Mössbauer study are evident of strong correlation between metallic fraction x in the composite and relative contribution of Fe ions in two different valence states (2- and 3-multiple-charged). It probably shows that phase composition of metallic component depends on the ratio between metallic and dielectric components. Temperature dependencies of DC resistivity described by exponential laws are characteristic for variable range hopping with Mott or Shklowski-Efros mechanisms. In the temperature range 77-300 K static I-V characteristics of the samples displayed non-ohmic character and were attributed to co-existence of Pole-Frenkel and ohmic (linear) laws. In so doing, the exponential contribution increased with the elevation of dielectric component. It was also exhibited negative magnetoresistance effect with squared-like magnetic field dependence that can be ascribed to tunneling of carriers between metallic particles.
Both real and imaginary parts of impedance in high-ohmic samples with x < 40 % in the frequency range from 0.1 to 10 kHz were not dependent on applied bias voltage, at least, for electric fields up to 4 V/cm. In the samples with x > 40 % the dramatic increase (up to 2-3 orders of magnitude) of capacitance modulus occurs at achieving some threshold value of bias voltage. The obtained increase of capacitance modulus with bias voltage is always accompanied by the decrease of real part of impedance. The value of threshold bias voltage decreases with the growth of metallic component content in the studied composites.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/2109 must be provided.

1. Ferromagnetic (Eu,Gd)Te/PbTe semiconductor heterostructures
2. Impedance, magnetoimpedance and magnetization of CoFeZr nanoclusters embedded into alumina matrix