Abstract:
Polycrystalline Co0.40Cu0.20Zn0.40GdxFe2-xO4 prepared by standard solid state
reaction technique sintered at various temperatures (1000, 1050, 1100 and 1150ºC) in
air for 3 hours. Structural, surface morphology and compositional analysis are
characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM)
respectively. The DC magnetizations as a function of applied magnetic field are
performed and increases with increasing applied magnetic field up to 0.1T, then
saturation occurs. The XRD patterns confirm the formation of spinel structure. The
lattice parameter, ao, increases with the Gd content. The bulk density (ρB) increases
and porosity (p) of the samples decreases with the increase of Gd content. The
average grain size increases with the Gd content, then decreases. The initial
permeability (μi
/) is found to increase with Gd content up to x=0.050 and then
decreases. The value of Q-factor increases with increasing Gd contents from x=0.000
to x=0.050, then it decreases. The real part of dielectric constant (ε/) initially decreases
rapidly in the low frequency region but at very high frequencies its value becomes so
small that it becomes independent of applied frequency. The dielectric loss tangent
(tanδE) decreases with the increase of Gd content due to the decrease of polarization.
The value of electric modulus (M/) is very low in the low frequency region. As
frequency increases the value of M/ increases and reaches a maximum constant value.
The value of Z/ (real part of impedance) and Z// (imaginary part impedance) decrease
with increasing frequency. The decrease in the values of Z/ and Z// shows that the ac
conductivity increases as the frequency increases and Z/ indicates dielectric relaxation
process. The value of AC conductivity (ζ AC) increases with AC applied field which
obeys the Jonschers power law.
