An anomalous conduction phenomenon in the Zn_1−xFeCrO₄Ni_xsystem

Abstract D.c. conductivity measurements carried out on ZnFeCrO4 have revealed a new conduction phenomenon. It was found that for temperatures above 360 K conduction is similar to that of semiconductors, obeying the relationship σ=σ0 exp (–E a/kT). At temperatures below 360 K, a transition occurs and the conductivity starts to increase with decreasing temperature. The rate of increase in conductivity is neither linear, as for metallic behaviour, nor abrupt, as for superconductors, but increases exponentially. The gradual replacement of Zn with Ni reduces this anomalous conduction phenomenon, until it completely disappears when all the Zn has been replaced by Ni.