Anomalous dielectric behavior in nanocrystalline gamma-Fe2O3

The measurements of electric capacities and dielectric loss angles for nano crystalline gamma-Fe2O3 under air and vacuum atmospheres have been conducte d by using ac LRC method, and the conductivity and the polarization relaxat ion time have also been calculated from the frequency spectra of real and i maginary parts of the dielectric constants. The anomalous dielectric behavi or implies the existence of two kinds of polarization mechanisms with diffe rent relaxation times, which are caused by the defects and the dangling bon ds in the interlaces, respectively. The experimental and calculated results indicated that the polarization loss and thf! conductance loss are dominan t in air atmosphere and vacuum, respectively.