Abstract:
MnJ_xZnxFe204 (X=O, 0.2, 0.4, 0.5, 0.6), MnO.5ZnO.5_yCayF'e204 (y=OJ, 0.2),
MnO.5ZnO.5_yMgyFe204 (y=OJ, 0.2) and MnO.5ZnO.5_yTiyF'e204 (y=O.l, 0.2) ferrites are
prepared using conventional solid state reaction technique. The samples are sintered at
two different temperatures (l200°C and 1300°C) in air for I hour. Structural and surface
morphology are studied by x-ray diffraction (XRD) method and high resolution optical
microscopy respectively. The magnetic properties of these ferrites are characterized by
frequency (I kHz-13MHz) and temperature dependence complex permeability
measurements. DC magnetizations (M) of all samples are measured using the
Superconducting Quantum Interface Device (SQUID) magnetometer.
The XRD patterns of all samples clearly indicate the formation of spinel structure. The
change in lattice parameter can be explained on the basis of the ionic radii. The grain
size increases with increasing Zn content in MnJ_xZnxFe204 as well as increase in
density. Grain size decreases when Zn is substituted by Ca or Ti but increases when Zn
substituted by Mg. Both real part of initial permeability, Ii: and bulk density, PB increase
with increasing Zn content in MnJ_xZnxFe204 up to x = 0.5 and beyond x = 0.5, Ii:
decreases but PB increases. The decrease in Ii: beyond x = 0.5 is mainly due to the noncollinear
spin arrangements. Resonance frequency, j,., and Neel temperature, TN,
decrease as Zn content increases.
Both Ii: and PB decrease with the addition of Ca, Mg or Ti as a replacement of Zn in
Mn-Zn ferrites, however j,. increases. From the magnetization as a function of applied
magnetic field M(H), curves it is clear that at room temperature all samples are in
ferromagnetic state. The relative quality factor, Q, and saturation magnetization, Ms,
increase for Mg doped samples but those decrease for Ca or Ti doped samples. Neel
temperature, TN, increases as Ca, Mg or Ti content increases in Mn-Zn ferrites. Possible
explanation for the observed characteristics of microstructure, initial permeability, DC
magnetization, and Neel temperature of the studied samples are discussed.
