Electronic transport and I-V characteristics of polycrystalline LuFe2O4

We report on electronic transport at low electric fields and I-V measurements on a polycrystalline sample of LuFe2O4. The range of temperatures of our measurements (limited by the high resistivity of the sample at low temperatures) includes the range where dramatic nonlinear conductivity and phase transitions were reported in the past. The temperature dependence of the absolute thermopower, measured up to 400 K, exhibits the characteristics of the 3-D charge-ordering and the magnetic-ordering transitions; the temperature dependence of the resistivity, measured only up to room temperature, indicates activated transport. Using single, short current pulses we obtained perfectly linear I-V characteristics up to fields of ∼500 V/cm. The large nonlinearity of the d.c. I-V characteristics at high fields is typical of self-heating in samples with activated conductivity.