Investigation of frequency dependence permeability of Ca, Mg and Ti substituted Mn-Zn ferrites

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.