Improvement of Structural, Elastic, and Magnetic Properties of Vanadium-Doped Lithium Ferrite

In this work, we synthesized ultra-fine particles of lithium ferrites co-substituted with nickel (Ni) and cobalt (Co), following the formula Li0.5-x/2(Ni0.7Co0.3)xFe2.5-x/2O4 (0.0 ≤ x ≤ 0.8), using the low-temperature sol–gel auto-combustion method, to enhance electromagnetic interference (EMI) shielding effectiveness (SE) to address the growing concerns regarding EMI pollution in both technology and human health. XRD investigations demonstrated the formation of a single-phase spinel structure, with crystallite size “D” in the range of 136.26–100.40 nm. A reduction in “D” and lattice constant “a” was observed with the inclusion of Ni-Co, accompanied by an increase in porosity, strain, and dislocation density. DC electrical measurements revealed that direct current (DC) electrical conductivity “σdc” of spinel ferrites at room temperature diminishes up to x ≤ 0.4 with the lowest value (1.71 × 10−10 mho/cm) and then enhances with the escalation of doping content (x). As per Maxwell–Wagner’s model, the dielectric parameters, including the dielectric coefficient, dielectric loss, and tangent of loss, reduce with frequency escalation. The alternating current (AC) electrical conductivity “σac” revealed a direct proportionality with the Ni-Co content because of the enhancement of some free charge carriers and improved charge hopping mechanism. The frequency exponent (n) value increases from 0.65 to 0.78 by Jonscher’s Power law. Magnetic parameters such as saturation magnetization (Ms), remanence (Mr), coercivity (Hc), and squareness ratio (SR) have been measured from hysteresis loops. The observed highest value of Ms was 7.13 emu/g for the prepared ferrite with x = 0.8. The Hc value falls within a few hundred Oersted range, which is crucial for electromagnetic materials. The magnetoresistance was greater with applying a magnetic field than without it. The magnetic susceptibility “Xm” of all the synthesized spinel ferrites depicted a progressive mitigation as the temperature enhanced due to the disturbance of spin orientation at the Curie temperature (Tc). The noted Tc value of all samples was 413–353 K. This research highlights Ni-Co co-doped lithium ferrites ascribed with multifaceted functionalities, making them auspicious candidates for specific applications such as in high-frequency electromagnetic devices, RF devices, and microwave absorption.

Improved cut-off frequency in Gd/La doped NiZnCo ferrites

Structure and magnetic properties of Si-rich FeAlSiBNbCu alloys

Structural, morphological and magnetic properties of Al3+ substituted Ni0.25Cu0.20Zn0.55AlxFe2−xO4 ferrites synthesized by solid state reaction route

Structural and some magnetic properties of manganese-substituted lithium ferrites

Conference Organization

Structural, magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites

Influence of metalloid antimony on the physical properties of palladium-based half-Heusler compared to the metallic bismuth: A first-principle study

Spinel ferrites Li0.3Zn0.4MoxFe2.3–xO4 (x = 0.00, 0.01, 0.02, and 0.03) have been prepared by the sol–gel auto-combustion method. The crystal structure, surface morphology, and magnetic properties of the samples have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The analysis of XRD data confirms the formation of a cubic Fd-3m phase for the samples with x ≤ 0.02, while a small amount of impurity phases α-Fe2O3 and Li2MoO4 appears in the sample with x = 0.03. The lattice parameter increases at x ≤ 0.02, which indicates that the valence state of Mo ions is mainly trivalent. Both saturation magnetization (Ms) and initial permeability (μi) first decrease and then increase with increasing Mo content. The maximum initial permeability (μi) of 101 is observed at x = 0.03, which is associated with the appearance of the impurity phase α-Fe2O3 with high density. The Curie temperature increases first and then decreases with x increasing. The highest Curie temperature (Tc) of 360 °C is observed at x = 0.02, which may be suitable for higher-temperature soft magnetic materials.

Lithium ferrite (Li0.5Fe2.5O4) powder was prepared by solid state reaction method, which was finally pressed and sintered at 1150°C. The spinel structure of the lithium ferrite was confirmed by X-ray diffraction and grain size estimation was obtained from scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) confirmed the presence of primary and secondary absorption bands characteristic for spinel structure. The force constants were estimated using absorption bands for the lithium ferrite. Magnetization and dielectric studies were carried out for the sintered sample. Saturation magnetization (Ms) of 59.6 emu/g was achieved and variation of magnetization with temperature was used to identify the Curie temperature. The complex permittivity (e*) for the lithium ferrite sample was obtained for wide frequency range up to 3GHz and discussed based on available models. The Curie temperature was estimated around 480°C and verified from both magnetization versus temperature and dielectric constant versus temperature measurements.

We studied the dilute substitution effect on magnetic and transport properties in an unstable ferromagnet CeFe2 with a C15 cubic Laves-phase structure. In the Co substitution system Ce(Fe1-xCox)2 with x≤0.10, while the Curie temperature T c decreases with increasing the Co concentration, an antiferromagnetic ordering appears in the low temperature region for x≥0.05, and the transition temperature T o from ferromagnetic to antiferromagnetic states monotonously increases with increasing the Co concentration. On the other hand, in the Sc substitution system (Ce1-ySCy)Fe2 with y≤0.10, both the Curie temperature T c and saturation magnetization M s at 4.2 K gradually increase with increasing the Sc concentration. Despite the decrease in lattice parameter upon substitution in both the systems, an antiferromagnetic ground state is stabilized in Ce(Fe1-xCox)2, whereas a ferromagnetic ground state is stabilized in (Ce1-yScy)Fe2. These results indicate that the Fe 3d–Fe 3d ferromagnetic exchange interaction and the antiferromagnetic spin correlation arising from the Ce4f–Fe3d hybridization compete in CeFe2, and the enhancement/depression of the 4f-3d hybridization effect might make the ferromagnetic ground state in CeFe2 unstable/stable. Furthermore, Ce(Fe1-xCox)2 exhibited a negative giant magnetoresistance reaching about δρ/ρ= ∼60–65 % at 4.2 K, which is accompanied by a metamagnetic transition from antiferromagnetic to ferromagnetic states. The giant magnetoresistance effect is originated from the reconstruction of Fermi surface due to the collapse of the superzone gap after the metamagnetic transition.

Role of Cr3+ ions on the microstructure development, and magnetic phase evolution of Ni0.7Zn0.3Fe2O4 ferrite nanoparticles

Three titanomagnetite samples, of composition x=0.7, 0.9, and 1.0 (where x is the ulvospinel molecular fraction), were oxidized according to the method of Sakamoto et al., namely, wetgrinding followed by heating to 200–300°C. Like the samples of Sakamoto et al., our samples showed reversal of saturation magnetization during alteration of titanomagnetite to titanomaghemite. Our experimental results seem to be compatible neither with the ionic model of Verhoogen nor with the model of O'Reilly and Banerjee. The Curie point gradually increased and the lattice parameter decreased during low-temperature oxidation (titanomaghemitization). On heating above 300°C, the γ-titanomaghemites underwent high-temperature oxidation (unmixing into magnetite, pseudobrookite, which is formed only during heating to 600°C, and rutile phases). The unmixing results in a sudden increase in Curie point and decrease in lattice parameter and saturation magnetization. On further heating, the saturation magnetization reverses for a second time. Therefore, double self-reversal of remanent magnetization in naturally oxidized rocks is considered a real possibility.

Microstructure and magnetization study of Li and Li–Zn ferrites synthesized by an electron beam

Dense kiln-fired lithium ferrite ceramic blocks with values of 4πMs ranging from 3600 to 2600 G have been prepared with low microwave dielectric losses (tanδ<0.0005) and high remanence ratios [Br/(4πMs)>0.7]. These low dielectric losses were achieved by addition of MnO2 and annealing in an oxygen atmosphere after the ceramic body was fired. The lower 4πMs compositions were obtained by substituting titania for part of the iron oxide in the basic lithium ferrite formulation. A number of physical properties were evaluated and the results are presented. These include density, saturation magnetization and Curie temperature. In addition, properties useful for microwave latching applications such as the complex dielectric constant and hysteresis characteristics (i.e., remanent magnetization and coercive force) are included. The temperature variation of the hysteresis properties for selected compositions is also shown.