Abstract :
The magnetic and transport properties of nanocrystalline ZnxFe3−xO4 with x=0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0, respectively, fabricated by the sol–gel method have been investigated. Large magnetoresistance (MR) was observed and found to be originated both from the tunneling of the spin-polarized electrons across the adjacent ferromagnetic grains and the scattering by the canted spins at the grain surface near the grain boundaries. It has been revealed that the MR for the ZnxFe3−xO4 samples (x=0, 0.5 and 1.0) increases with the temperature decreasing from room temperature until a maximum is reached at around 55 K. Then a sharp drop occurs with the further decrease in temperature, regarded as a spin (cluster) glass transition. For the samples studied, a biggest low field (0.5 T) MR value of about 20% for x=0 at 55 K has been obtained. The mechanism of the MR behavior of the materials was discussed.
