Effective-medium theory of open-orbit inclusions

Abstract

We extend the effective-medium approximation for the electrical conductivity of a heterogeneous material to a nonsymmetric effective conductivity tensor. We apply it to a binary mixture of oriented crystallites in which one component has open orbits and the other does not. We calculate the transverse magnetoresistance as a function of field strength and orientation. The open-orbit magnetoresistance peaks that would be observed in a homogeneous sample persist in the mixture, but are broader and smaller. Nevertheless, when the product of the volume fraction $f$ of the open-orbit component and ${\ensuremath{\omega}}_{c}\ensuremath{\tau}$ is greater than unity, the peak height increases quadratically with field strength.