Temperature dependence of the electrical resistivity in insulating granular films under high pressure

Abstract

We have studied electrical resistivity of Co₄₃Al₂₄O₃₃ insulating granular films under high pressure. This material consists of nanometer-sized Co granules embedded in an Al-oxide matrix. in which electron tunneling between Co granules and electrical charging effect (Coulomb blockade) of Co granules plays an important role for the electrical conduction. The tunneling conductivity is enhanced by applying pressure. and the enhancement is more significant at low temperatures. The characteristic temperature dependence represented by logρ^∝T-1/2 is observed at high pressure up to 3.1 GPa. The proportional coefficient of logρ^∝T-1/2 relationship shows a clear tendency to decrease with increasing pressure. This behavior can be mainly interpreted by the suppression of charging effect. assuming that the Al-oxide matrix is more compressible than Co granules.