  This work is a contribution to the understanding of the electrical
resistivity in strontium ferromolybdate (SFMO) ceramics. It demonstrates that
an appropriate thermal treatment leads to the formation of dielectric SrMoO4
shells at the surface of SFMO nanograins. In samples without SrMoO4 shells, the
sign of the temperature coefficient of resistance changes with increasing
temperature from negative at very low temperature to positive at higher
temperatures. Samples exhibiting a negative temperature coefficient contain
SrMoO4 shells and demonstrate a behavior of the resistivity that can be
described in terms of the fluctuation-induced tunneling model, and near room
temperature the conductivity mechanism converts to a variable-range hopping
one. The results of this work serve as a starting point for the understanding
of the low-field magnetoresistance which is very promising for spintronic
device application.
