Canadian Journal of Physics · 1979 · 13 citations · 2 references
Natural SciencesMaterials EngineeringMaterials ScienceMaterials ChemistryMaterials PhysicsTransport PhenomenaConductive MaterialsCurie TemperatureElectrical ConductivityPhase TransitionsThermal Properties Of MaterialsThermoelectric MaterialsConductionConduction BandElectrical Conductivity MeasurementsElectrical Transport PropertiesElectronic ConductionGadolinium-based AlloysHopping ConductionTemperature Effects On Conductivity
Thermoelectric power [Formula: see text] and electrical conductivity (σ) of Gd 3 Fe 5 O 12 (gadolinium iron garnet GdIG) have been reported in the temperature range 500 to 1200 K. [Formula: see text] remains almost constant between 600 and 1100 K but it increases with decrease of temperature in accordance with the relation[Formula: see text]Conductivity changes by a factor of five near the ferrimagnetic Curie temperature (T e = 564 K). The log σ vs. T −1 curve also has a break at 900 K. Besides this jump and break the log σ vs. T −1 plot is linear and slopes of these lines correspond to activation energies of 0.55 eV for T < 560 K, 0.75 eV for the temperature range 575–900 K, and 0.92 eV between 900 and 1200 K. It has been concluded that electric conduction up to 1200 K in this compound is extrinsic. Between 575 and 1200 K it is due to hopping of holes from Fe 4+ to Fe 3+ sites and below 560 K it is due to the band conduction of holes in the valence (O 2− , 2p) band.
2