Electrical properties of amorphous (Co45Fe45Zr10)x(Al2O3)1−x nanocomposites

The electrical properties of (Co45Fe45Zr10)x(Al2O3)1−x granular nanocomposites have been studied. The concentration dependences of electrical resistivity are S-shaped (in accordance with the percolation theory of conduction) with a threshold at a metallic component concentration of ∼41 at. %. An analysis of the temperature behavior carried out in the range 300–973 K revealed that structural relaxation and crystallization of the amorphous phase are accompanied by a decrease in the electrical resistivity of the composites above the percolation threshold and by its increase below the percolation threshold. For metallic phase concentrations x<41 at. %, variable range hopping conduction over localized states near the Fermi level was found to be dominant at low temperatures (77–180 K). A further increase in temperature brings about a crossover of the conduction mechanism from Mott’s law ln(σ) ∝ (1/T)1/4 to ln(σ) ∝ (1/T)1/2. A model of inelastic resonance tunneling over a chain of localized states of the dielectric matrix was used to find the average number of localized states involved in the charge transport between metallic grains.