S.I. El-dek

Preparation and characterization of nanometric Mn ferrite via different methods

The structure and magnetic properties of MnFe(2)O(4) ferrites have been investigated using five different preparation methods, including the ceramic technique, flash combustion, co-precipitation, sol-gel and citrate methods. The characteristics of one sample prepared by different methods have been studied to select the better method, i.e.xa0the one that is the simplest and does not require an elaborate instrumental set-up. The results indicated that the citrate method gives the lowest value for the lattice parameter and particle size (14.1xa0nm), while the highest values are obtained with the ceramic method. The smallest nanosizes were obtained in the citrate and flash methods (14.1 and 40.7xa0nm, respectively).

The memory effect of Dy2.8Sr0.2Fe5O12(DySrIG) nanoparticles

Dy2.8Sr0.2Fe5O12 (DySrIG) was prepared using the citrate–nitrate auto-combustion method. Single phase garnet with cubic structure was obtained at 1100u2009°C. Thermal hysteresis (heating–cooling) study was performed for the following physical properties: crystal structure using x-ray diffraction (XRD); magnetic susceptibility using Faraday’s method; dielectric measurements including dielectric constant as well as ac conductivity using an LCR meter. The results of the study reveal hysteresis loops in all the parameters which agree with those appearing in differential scanning calorimetry (DSC), and the former were interpreted according to the accompanying changes in the structural characterizations. The study clarifies that the investigated nanoparticles of DySrIG possess an electric memory effect with thermalization, where their dielectric parameters have sensitive changes with temperature in the range 25–400u2009°C and return to their original values at room temperature again. Accordingly, DySrIG could be recommended in thermal electric sensor applications (thermistors).

Does Ti+4 Ratio Improve the Physical Properties of CdxCo1−x+tTitFe2−2tO4?

The microstructure and magnetic properties of Ti substituted CoCd ferrites of the general formula CdxCo1−x+tTitFe2−2tO4, x = 0.20, 0.00⩽t⩽0.25 have been reported. The ferrite samples were prepared by standard double sintering ceramic technique and structural analysis was carried out using X‐ray diffraction. The spinel structure is confirmed for all concentration. Some physical properties (such as lattice parameter, density and porosity) have been also calculated. Temperature and magnetic field dependence of susceptibility is illustrated for all Ti contents. Both experimental and theoretical values of the effective magnetic moment were increased with increasing Ti content. The Curie temperature increases with the addition of Ti up to t = 0.15 after which it decreases. The effect of mechanical pressure on the dc resistivity at room temperature enhances the use of the samples in some applications.