On the conductivity of magnetite below the Verwey transition

Using existing data, the authors emphasise that in the range T v >T> approximately T v /2 the electrical conductivity sigma of Fe 3 O 4 , and some other mixed-valence oxides, is described better by sigma varies as exp(T) than by an Arrhenius law. A possible explanation of this dependence is offered, based on incoherent tunnelling of electrons between neighbouring sites.