Phase transformation, dielectric and magnetic properties of Nb doped Bi0.8Sr0.2FeO3 multiferroics

Bi0.8Sr0.2Fe1-xNbxO3 (x = 0.0, 0.05, and 0.10) multiferroics were prepared by solid state reaction method. X-ray diffraction and Rietveld analysis show that crystal structure is rhombohedral for x = 0.0, 0.05 samples and triclinic for x = 0.10 sample. These samples showed dispersion in dielectric constant (epsilon) and dielectric loss (tan delta) values at lower frequencies. For x = 0.05 sample, both epsilon and tan d are lower than for Bi0.8Sr0.2FeO3 sample indicating its high resistivity. For x = 0.10 sample, the value of epsilon is enhanced which may be due to formation of stronger dipoles in triclinic structure. Temperature dependence of frequency exponent s of power law suggests that correlated barrier hopping (CBH) model is applicable at lower temperatures and quantum mechanical tunneling model is appropriate at higher temperatures for describing the conduction mechanism in x = 0.0 and x = 0.05 samples; while in x = 0.10 sample, CBH model is appropriate in studied temperature range. Significant enhancement observed in magnetization for x = 0.10 sample is due to the structural phase transition from rhombohedral to triclinic caused by Nb substitution. For this sample, values of remnant magnetization (M-r) and coercive field (H-c) are 0.155 emu/g and 2.695 kOe, respectively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4728981]