Abstract:
Polycrystalline MnxFe3-xO4 (0.1≤x≤0.9) ferrites were prepared by the standard solid state
reaction technique. The samples were sintered at various temperatures (1250ºC, 1300ºC
and 1350ºC) in air for 5 hours. Structural and surface morphology were studied by Xray
diffraction and optical microscopy respectively. The magnetic properties of these
ferrites were characterized with high frequency (1 kHz-15 MHz) complex initial
permeability. The effects of microstructure, composition and sintering temperatures on
the complex initial permeability of MnxFe3-xO4 ferrites are discussed. A possible
correlation of sintering temperature with grain size and density of the material is also
discussed.
Lattice parameter decreases with the increase of Mn+2 content for all
compositions. The decrease in lattice parameter with increasing Mn+2 content can be
explained on the basis of the ionic radii. The microstructural study shows that grain size
increases with increasing Mn+2 content for a particular sintering temperature. Both the
theoretical and experimental density of the samples increases and the corresponding
porosity of the samples decreases with increasing of Mn+2content. The density of the
polycrystalline MnxFe3-xO4 compositions increases as the sintering temperature increases
from 1250ºC to 1300ºC and above 1300ºC the density decreases. On the other hand,
porosity of the sample decreases with increasing of sintering temperature up to 1300ºC
and above 1300ºC the porosity increases.
The initial permeability value increases with increasing Mn+2 content, because
the average grain size increases with increasing Mn+2 content for the polycrystalline
MnxFe3-xO4 compositions. The real part of the initial permeability remains fairly
constant in the frequency range up to some critical frequency characterized by the onset
of resonance. At these frequencies, after a small rise, the curves drop rapidly. The
relative quality factor (Q) is found to increase with increasing Mn+2content. The
magnetization as a function of applied magnetic field, M(H) for various Polycrystalline
MnxFe3-xO4 samples at room temperature (300K) were measured. DC electrical
resistivities of the samples at room temperature as function of Mn+2 content were also
measured.
