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To observe the impact of the annealing time on the alloy structure and ultra-soft magnetic properties of Fe75.5Si13.5Cu1Nb1B9, the alloy was annealed in a controlled way in the temperature range 475 - 600°C for different annealing time from 5 to 30 min. Amorphosity of the ribbon and nanocrystalline state was evaluated by X-ray diffraction. Grain size and Si content increase with increasing annealing temperature and time; on the other hand lattice parameter decrease with increasing annealing temperature and time. The maximum permeability was observed at annealing temperature Ta = 525°C for 15 min, and thereafter it starts to decreases. Saturation magnetization increases with annealing temperature Ta for the samples and finally decreases during annealing at a temperature much higher than peak crystallization temperature. The results of the experimental observations are explained on the basis of existing theories of nanocrystalline amorphous metallic ribbons. [ABSTRACT FROM AUTHOR]

Polycrystalline NiFe2O4 samples were prepared from analytical grade powder of NiO and Fe2O3 by conventional double sintering technique. The samples were sintered at 1000 - 1400°C. The scanning electron micrographs (magnification × 10000) of the samples revealed that the grain size increases and the porosity decreases with the increase in sintering temperature. These changes in microstructure, grain size and porosity with sintering temperature have great influence on the magnetic properties of NiFe2O4. Complex permeability (μ') over the frequency range from 1 kHz to 13 MHz for the samples at different sintering temperatures (1000-1400°C) has been observed. Variation of permeability with the applied temperature has been observed at various sintering temperature from which Curie temperature have been calculated. Decreased value of Curie temperature (Tc) has been found with the increase of sintering temperature. [ABSTRACT FROM AUTHOR]

The effects of Li2O additives on the structural, magnetic and electrical properties of Ni0.5Mg0.5 Fe2O4, prepared by conventional double sintering ceramic technique were investigated. The X-ray diffraction (XRD) pattern of the prepared samples showed single phase cubic spinel structure. Variation of lattice parameter has been observed with the variation of Li2O content. The enhancement of bulk density has been observed for 2 mol% Li2O additive, but further increase in Li2O concentration, these values decrease. Enhancement of initial permeability (µ') have been observed for the sample with 2 mol% Li2O additives while it decreases for higher concentration of Li2O. The Curie temperature is found to decrease with the increase in Li2O additive. The resistivity increases with increasing additive content and showed a significant dispersion with frequency, which is the normal ferromagnetic behavior. The dielectric constant (є') measurement showed the normal dielectric behavior of spinel ferrite. Possible explanation for the observed features are discussed. [ABSTRACT FROM AUTHOR]