Study of Hard Magnetic Properties of Hexagonal Ferrites Using Magnetite from Cox's Bazar Beach Sand with the Addition of Rare-earth Oxides

Abstract

The structural and magnetic properties of Sr- and Ba-hexaferrites with magnetoplumbite structure of composition (MeO)1-x (La203)x 5.7 Fe203, where x = 0.00, 0.04, 0.08 and MeO. 5.7 Fe203+ [0.7wt% CaO +0.3wt% SiO2] and where Me = Sr and Ba prepared by standard ceramic technology at different sintering temperature using magnetite from Cox's Bazar beach sand, Bangladesh have been investigated in the present research work. The detailed work carried out by the measurement of density, porosity, identification of crystalline structure through X-ray diffraction (XRD) technique, unit cell volume, lattice parameters, Curie temperature, microstructure analyses of the samples following Scanning Electron Microscope (SEM), permeability, resistivity and study of hysteresis parameters viz, saturation magnetization, remanent magnetization and coercivity using quantum design physical property measurement system (PPMS) vibrating sample magnetometer (VSM). The density of the sintered hexaferrite samples has been found to be dependent with the additives and the sintering temperature. During the study it has been observed that the porosity and the lattice parameter a and c of the hexaferrites are also to be varied with addition of La03 and with the simultaneous addition of (CaO + SiO2). The Curie temperature of Sr-hexaferrites has been found to be almost unchanged with the addition of La203 but with the addition of CaO and SiO2 the Curie temperature has been found to be increased a little. At the same time Curie temperature of Ba-hexaferrite samples decreases with the addition of La203 and increases with the simultaneous addition of (CaO + SiO2). The phase identification and hexagonal shape particle morphology has been confirmed by XRD analyses of hexaferrites. SEM study of the SrM and BaM hexaferrites show that the particles are of elongated and irregular shaped and the average grain size decreases with the addition of La2O3. Throughout the investigation it has also been found that grain size increases with increasing sintering temperature. The hysteresis measurements show that the additives have a significant effect of the hysteresis parameters of the hard ferrites. In the case of Sr-hexaferrites the value of saturation magnetization, M increases first with the La2O3 addition and then decreases. But in the case of BaM the value of M and coercivity has been found to be increased with the La2O3 addition. In our observation it has been found that the magnetic properties of the sintered barium and strontium hexaferrite samples having off-stoichiornetric composition increases remarkably with the addition of La2O3 and (CaO + SiO2).