Influence of Zn(Ⅱ) on the structure, magnetic and dielectric dynamics of nano-LaFeO_3

摘要

We demonstrate in detail the influence of divalent non-magnetic metal ion Zn on the structural, magnetic ordering as well as the dielectric dynamics of nano-sized LaFeO_3. Introduction of Zn at Fe site distorts the FeO_6 octahedron near it evidencing from a shift in the most intense peak towards lower angle. Subsequent broadening of peaks signifies a lower particle size which is further supported by micrographs. With field history, temperature-dependent magnetization shows that the doped samples acquire a non-ergodic state at low temperature and the incompleteness of the phase transition even at very high temperature. The isothermal magnetization depicts a significant increase in magnetization at higher field with a decrease in coercivity. Extensive impedance and electrical modulus analysis are carried out to know the exact conduction process and relaxation mechanism adopted by the doping system. Impedance spectra reveal a non-Debye type of relaxation mechanism and with increase of Zn concentration and temperature, grain boundary effect dominates over grain effect. This grain and grain boundary effect is further confirmed through electrical modulus Nyquist plots. The activation energy values of grain and grain boundary are 0.37 eV and 0.47 eV for ⅹ = 0.1, 0.37 eV, 0.40 eV for ⅹ = 0.2 and 0.28 eV, 0.38 eV for ⅹ = 0.3, respectively. Accordingly, the doping system agreed with a p-type polaronic hopping. Furthermore, the frequency-dependent electrical conductivity data are explained in the framework of both Jonscher power law and Jump relaxation model.