Electronic transport and conduction mechanism transition in La_(1/3)Sr_(2/3)FeO_3 thin films

摘要

We report on the electronic transport properties of epitaxial La_(1/3)Sr_(2/3)FeO_3 films using temperature dependent resistivity, Hall effect, and magnetoresistance measurements. We show that the electronic phase transition, which occurs near 190 K, results in a change in conduction mechanism from nonadiabatic polaron transport at high temperatures to resistivity behavior following a power law temperature dependence at low temperatures. The phase transition is also accompanied by an abrupt increase in apparent mobility and Hall coefficient below the critical temperature (T~*). We argue that the exotic low temperature transport properties are a consequence of the unusually long-range periodicity of the antiferromagnetic ordering, which also couples to the electronic transport in the form of a negative magnetoresistance below T~* and a sign reversal of the Hall coefficient at T~*. By comparing films of differing thicknesses, stoichiometry, and strain states, we demonstrate that the observed conduction behavior is a robust feature of La_(1/3)Sr_(2/3)FeO_3.