dc transport properties and resistance fluctuation processes in Sr2FeMoO6 polycrystalline thin films

We performed transport measurements and voltage noise analysis on Sr2FeMoO6 thin films, in zero applied magnetic field as a function of temperature T, down to 10 K. The samples, grown by pulsed laser deposition on SrTiO3 substrates, showed a negative resistivity thermal coefficient and, at T<50 K, the observed temperature dependence of resistivity and the I-V curves were correctly described by the fluctuation-induced tunneling model which assumes the presence of intergranular tunneling of charge carriers. Moreover, the analysis of the low temperature resistance fluctuation processes, pointed out the presence of a voltage noise component independent of the frequency within the whole investigated bandwidth with a spectral density directly proportional to the square of the bias current. We interpreted this unusual behavior as a possible consequence of tunneling intergranular processes.