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 similar to41 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(sigma) proportional to (1/T)(1/4) to ln(sigma) proportional to (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. (C) 2004 MAIK Nauka/Interperiodica.