Synthesis and characterization of La_(0.75)Ca_(0.15)Sr_(0.05)Ba_(0.05)MnO_3-Ni_(0.9)Zn_(0.1)Fe_2O_4 multiferroic composites

摘要

In the present work, we report on structural, dielectric, impedance spectroscopic studies and magne-toelectric properties of (1 -x) La_(0.75)Ca_(0.15)Sr_(0.05)Ba_(0.05)MnO_3 (LCSBMO) + (x) Ni_(0.9)Zn_(0.1)Fe_2O_4 (NZFO) (x=0.0, 0.1, 0.2, 0.4, 0.6, 0.8 and 1.0) composites. The composites were prepared by the solid state reaction route. The coexistence of a cubic spinel NZFO phase and a tetragonal LCSBMO phase in the composites is confirmed by the X-ray diffraction measurement. Scanning electron microscopy images reveal that NZFO particles were distributed non-uniformly with some porosity in the LCSBMO matrix. Frequency dependent dielectric constant shows usual dielectric dispersion behavior, which may be attributed to the Maxwell-Wagner type interfacial polarization. At higher frequencies ( ≥ 10~5 Hz), due to electronic and ionic polarizations only, the dielectric constant is independent of frequency. Complex impedance shows semicircular arc due to the domination of grain boundary resistance and electric modulus confirms the presence of hopping conduction. The AC conductivity (σ_(AC)) obeys the power law and the linearity of log ω~2 versus log σ_(AC) plots indicates that the conduction mechanism is due to small polaron hopping. Low frequency dispersion in permeability is due to domain wall motion and the frequency stability of permeability indicates that the arrangement of the magnetic moment in the polarization process can keep up with the external field. The maximum magnetoelectric voltage coefficient of ～40 mV Oe~(-1) cm~(-1) for x=0.8.