Nitendar Kumar

Study of magnetization and crystallization in sputter deposited LiZn ferrite thin films

LiZn ferrite films of composition Li00.5−x/2Mn0.1ZnxFe2.35−x/2O4 with x=0.32 were rf sputter deposited on fused quartz substrates at ambient temperature. The as-deposited films were found by x-ray diffraction to be amorphous but magnetic, and showed large high field susceptibility. The films were studied after they were annealed at various temperatures up to 850 °C. It was observed that the films crystallize upon annealing and the value of the saturation magnetization increases with annealing temperature. The high field susceptibility, on the other hand, decreases with increasing anneal temperature. The measured ferromagnetic resonance spectra of these films indicated that the films consist of at least two different magnetic materials. A significant portion in the film crystallizes and the value of saturation magnetization of this portion tends to the bulk value as annealing temperature is increased. However, a small portion of the film remains in a highly defective state all through, even up to annealing...

Dielectric and magnetic properties of polycrystalline cobalt‐substituted LiTi ferrites

The electric, dielectric permittivity, loss tangent, microwave power absorption, and hysteresis loop parameters were studied on a series of cobalt‐substituted lithium titanium ferrites. The experimental results indicate that cobalt substitution affect all these parameters. The observed dispersion in conductivity and dielectric permittivity with frequency and temperature are in accordance with Maxwell–Wagner model while the microwave and hysteresis loop properties can be interpreted with the help of Dionne’s exchange isolation model.

Elastic behaviour of Zn-substituted LiMg and LiMgTi ferrites

Abstract Two series of Zn-substituted LiMg and LiMgTi ferrites were prepared by the solid state reaction method with a view to investigate their elastic behaviour. The elasticity studies were undertaken by measuring the ultrasonic velocities by adopting the pulse transmission technique. As the materials under investigation are porous, the experimentally obtained elastic moduli such as Youngs moduli, rigidity moduli, Poissons ratio have been corrected to zero porosity using Ledbetter and Dattas formulae. It has been observed that all the elastic moduli decrease continuously with increasing dopants concentration. Using the experimental data, other important elasticity parameters such as the Debye temperature, V l /ρ and V s / ρ have also been evaluated and their variation with dopants concentration has been explained qualitatively.

Effect of MgTi and ZnTi substitutions on electrical and magnetic properties of Li ferrite

Abstract Simultaneous substitutions of varying amounts of Zn2+ Ti4+ and Mg2+ Ti4+ have been incorporated into Li ferrite. A comparative study of the magnetic and electrical properties of the two series has been carried out. Diverse trends of variation of some of the magnetic parameters have been observed for the two sets of ferrite samples. The observed behaviour is explained on the basis of the site preference of substituent ions and their effect on the microstructural developments in the material.

Electrical transport properties of germanium-substituted lithium ferrites

Electrical conductivity (σ) and thermopower (S) studies of polycrystalline germanium-substituted lithium ferrites having different compositions were made in the temperature range 400–1000 K. The composition dependence of electrical conductivity and thermopower has been discussed. On the basis of the sign of the Seebeck coefficient, all the samples under investigation have been classified as n-type semiconductors. Using the temperature variation of charge carrier concentration and mobility, the conduction mechanism in these ferrites is suggested.

Mössbauer studies of Ag ion-irradiated NiMn0.05Fe1.95O4 ferrite

Abstract The swift heavy ion-irradiated nickel manganese ferrite system has been studied with the Mossbauer technique. The NiMn 0.05 Fe 1.95 O 4 system was synthesized using a solid state reaction technique. To ensure the single-phase spinel structure of the system powder X-ray diffraction has been performed. The powdered samples were irradiated with a 190 MeV Ag ion beam at various fluences in the range of 1×10 11 – 1×10 13 ions/cm 2 . Mossbauer studies have been performed on pristine and irradiated samples. The spectra obtained were resolved into two sextets and a paramagnetic doublet for all the samples using the NORMOS program. From the observation of the results obtained we can say that the increase in the paramagnetic doublet with the irradiation is due to ion-induced disorder.

Electrical conductivity and thermoelectric power studies of aluminium-substituted lithium ferrites

Electrical conductivity (σ) and thermoelectric power (S) of polycrystalline aluminium-substituted lithium ferrites of various compositions have been investigated as a function of composition and temperature. The Seebeck coefficient is negative for all the ferrites under investigation showing that these ferrites behave as n-type semiconductors. The values of charge carrier concentration have been computed from Seebeck coefficients. All the ferrites are found to exhibit clearly and well-defined transitions near the Curie temperature in Seebeck coefficient conductivity and carrier concentration vs. temperature plots. Activation energies of all the samples are calculated. An attempt is made to explain the conduction mechanism in these ferrites.

Circular array of microstrip circular patches printed on LiTiMg ferrite substrate

A four elements circular array of microstrip circular patches presented which is printed on LiTiMg ferrite substrate. Comparison of radiation patterns between Quartz substrate and polycrystalline ferrite substrate (LiTiMg ferrite) circular patch microstrip antenna (CPMAA) shows the effective use of Li ferrites in antenna applications in X-band of electromagnetic wave spectrum. In this work we also synthesized the polycrystalline LiTiMg ferrite of 2200 Gauss 4πMs and characterize their electric and magnetic properties as a substrate for CPMAA.

Linear Array of Microstrip Rectangular Patches on Magnetically Biased LiTiZn Ferrite Substrate at 10 GHz

Abstract The effect of magnetic biasing on the performance of four element linear array of microstrip rectangular antenna (RPMAA) on LiTiZn ferrite substrate at 10 GHz is discussed. In this study, we synthesized the polycrystalline LiTiZn ferrite of 2200 Gauss 4πMs and characterized its electric and magnetic properties as a substrate for RPMAA. The total field patterns for single patch and array geometry have been computed and plotted using vector wave technique and pattern multiplication approach. It is observed that the array geometry is suitable for controlling directive beam by the external magnetic field. Results show that the applied magnetic field compares and distributes the radiated power between the main lobe and side lobes.

ELASTIC BEHAVIOR OF GERMANIUM-SUBSTITUTED LITHIUM FERRITES

The longitudinal and shear wave velocities of germanium-substituted lithium ferrites were determined at room temperature by the pulse transmission technique. Youngs (E) and rigidity (n) moduli have been corrected to theoretical density by a power equation. The zero porous corrected values of both the elastic moduli (Youngs and rigidity) are found to increase with increasing germanium concentration. A linear relationship between the Debye temperature and the average sound velocity has also been observed.