Spin-polarized electron transport in highly reduced MgFe2O4-delta

Spin-polarized electron transport is important for spintronics. In this study, MgFe2O4 compound has been reduced by using metallic sodium as a reducing agent and high concentration of oxygen vacancies has been induced in the compound, and the electron transport behavior of a highly-reduced MgFe2O4-delta has been studied in detail. It is found that the room-temperature electrical resistivity of MgFe2O4-delta is decreased by almost 6 orders of magnitude when it is rich in oxygen vacancies (concentration: similar to 10(21) /cm(3)). Based on the density functional theory, the band calculations show that the oxygen vacancies can introduce mid-gap states below the upper Hubbard band. The electronic states around the Fermi level are mainly composed of spin-down Fe 3d orbits, indicating highly spin-polarized carriers. Combining with the analysis of the temperature-dependent resistivity, it is demonstrated that the electron transport behavior is mainly dominated by the model of variable-range hopping. It is suggested that the low-temperature reduction is an efficient way to realize the heavily doping of carriers without crystal structure destroying, which provide a new way to turn the electron transport behavior and broaden a potential application of spinel ferrites in spintronic devices.