Thickness-dependent transport properties of Sr4Fe6O13 epitaxial thin films

High-quality epitaxial thin films of Sr4Fe6O13 have been deposited on NdGaO3(001) substrates by pulsed laser deposition. The transport properties have been characterized by impedance spectroscopy. The temperature dependence of conductivity suggests a mechanism of adiabatic hopping by small polarons, in agreement with previous results in bulk samples. The transport properties show a clear dependence on the film thickness with the thinner films (10 nm) presenting conductivity values in oxygen one order of magnitude higher than the thicker ones (313 nm). We correlate this behaviour with the thickness dependence of the epitaxial strain.