Dc transport properties and resistance fluctuation processes inSr2FeMoO6polycrystalline thin films

Abstract

We performed transport measurements and voltage noise analysis on ${\mathrm{Sr}}_{2}\mathrm{Fe}\mathrm{Mo}{\mathrm{O}}_{6}$ thin films, in zero applied magnetic field as a function of temperature $T$, down to $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The samples, grown by pulsed laser deposition on $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ substrates, showed a negative resistivity thermal coefficient and, at $T<50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the observed temperature dependence of resistivity and the $I\text{\ensuremath{-}}V$ 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.