MgFe2O4 Ferrite Research Articles

Magnetic and dielectric behavior of terbium substituted Mg1−xTbxFe2O4 ferrites

The effects of concentration of terbium (Tb) on ferromagnetic resonance (FMR), relative initial permeability, morphology, and dielectric properties of MgFe2O4 ferrites were studied. It is found that FMR line-width and FMR position of magnesium–terbium (Mg–Tb) ferrites are found to fluctuate with the increase of Tb-content. The increase in FMR line-width is attributed to the charge transfer mechanism and inhomogeneity in the samples (TbFeO3). The relative initial permeability decreases gradually as a function of Tb-content. The magnetic loss factors of substituted samples exhibit decreasing behavior in the frequency range 1kHz to 10MHz. Terbium substituted samples have lower dielectric constant as compared to the pure MgFe2O4 ferrite. The decrease in dielectric constant is attributed to the retardation in electron exchange mechanism caused by lockup among iron and terbium ions. An irregular behavior of the dielectric loss is found, which is related to the hopping probability of charges in these ferrites. A decrease in the ac conductivity is observed beyond 8MHz and this corresponds to the occurrence of dielectric loss. The low magnetic and dielectric behavior makes these ferrite materials suitable for their applications in microwave devices.

Soft mechanochemical synthesis of MgFe2O4 nanoparticles from the mixture of α-Fe2O3 with Mg(OH)2 and Fe(OH)3 with Mg(OH)2

The influence of long term soft milling of a mixture of (1) Mg(OH)2 and α-Fe2O3 and (2) Mg(OH)2 and Fe(OH)3 powders in a planetary ball mill on the reaction synthesis of nanosized MgFe2O4 ferrites was studied. Soft mechanochemical reaction leading to formation of the MgFe2O4 spinel phase was followed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and magnetisation measurements. The spinel phase formation was first observed after 5 h of milling and its formation was completed after 15 h in case (2). The synthesised MgFe2O4 ferrite had a nanocrystalline structure with a crystallite size of about 10 and 15 nm respectively for cases (1) and (2). Measurements after 15 h of milling show magnetisation values of 15·23 and 10·14 J T–1 kg–1 respectively for cases (1) and (2).

Mechanochemical synthesis of stoichiometric MgFe2O4 spinel

The influence of long-term milling of a mixture of (1) MgO and α-Fe2O3, (2) MgCO3, and α-Fe2O3, and (3) Mg(OH)2 and α-Fe2O3 powders in a planetary ball mill on the reaction synthesis of nanosized MgFe2O4 ferrites was studied. Mechanochemical reaction leading to formation of the MgFe2O4 spinel phase was followed by electron microscopy, (SEM and TEM), X-ray diffraction and magnetization measurements. The spinel phase was observed first in cases (1) and (2) after 5 h of milling, and its formation was observed in all cases after 10 h. The synthesized MgFe2O4 ferrite has a nanocrystalline structure with a crystallite size of about 11, 10, and 12 nm, respectively for cases (1)–(3). Magnetic measurements after 10 h of milling show magnetization values of 19.8 J/(Tkg), 23.5 J/(Tkg) and 13.8 J/(Tkg), respectively for the cases (1)–(3).

The influence of Sn4+ and/or Mo6+ ions on the structure, electrical and gas sensing properties of Mg‐ferrite

AbstractThe influence of partial replacing of Mg and Fe ions by Sn and Mo ions, respectively, on the structural and conductivity properties of MgFe2O4 ferrite is studied by means XRD, SEM and resistivity measurements. Four compositions of ferrites, Mg1–xSnxMoyFe2–yO4 (x = 0, 0.1 and y = 0, 0.02) were prepared by autocombustion, starting from metal nitrates. The presence of foreign phase was evidenced in the Sn containing ferrite. Also, Sn and Mo ions induced structural changes regarding grain size and porosity. The finest granulation, of about 100 nm, was observed in the Sn containing sample, Mg0.9Sn0.1Fe2O4 having the highest porosity. The electrical resistivity increased with about two orders in magnitude when Sn4+ ions partially substituted Mg in MgFe2O4 ferrite. All samples were tested for sensing properties to reducing gases: ethanol and acetone. The gas sensitivity considerably depends on the kind of substituent ion and the type of gas to be detected. All the ferrites were more sensitive to acetone than to ethanol. It was revealed that among all ferrites tested, Mg0.9Sn0.1Fe2O4 is the most sensitive to acetone. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Microscopic and Macroscopic Magnetic Properties of the MgAlxCrxFe2 - 2xO4Spinel Ferrite System

To determine the influence of the substitution of Al3+ and Cr3+ for Fe3+ in MgFe2O4 ferrites on the structural and magnetic properties, the MgAl x Cr x Fe2 − 2x O4 (x = 0.0–0.8) spinel systems were studied by using the X-ray diffraction analysis, magnetization in strong fields, magnetic susceptibility in weakly variable electric fields, and Mossbauer spectroscopy. Unlike previous investigations, it was discovered that a half of Al3+ occupies tetragonal positions. The system forms a noncollinear spin structure and a central paramagnetic doublet is superimposed over the magnetic sextet in the Mossbauer spectrum (0.5 > x > 0.2). The dependence of the magnetic susceptibility on temperature reveals the normal ferromagnetic properties of the material.