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Ni0.5Zn0.5Fe2O4 particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show superparamagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure.

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A novel kind of microwave absorption composite in Ku-band with low cost, low density and strong absorption was prepared through Bio-template carbonization and solvothermal method. The phase structures and morphologies of the composite had been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of carbonized kapok fibers and Fe3O4/kapok fibers were measured by vector network analysis (VNA). When the sample thickness is 1.5 mm, the Fe3O4/kapok fibers have an optimal absorption peak value of about -24.1 dB at 17.4 GHz and its effective absorption bandwidth lower than -10 dB reaches 2.4 GHz (from 15.6 to 18.0 GHz). The reflection loss results indicate that the Fe3O4/kapok fibers possess higher microwave absorption in the Ku-band. A possible mechanism of the improved microwave absorption performance of the composite was discussed. [ABSTRACT FROM AUTHOR]

M-type hexaferrites BaFe12-2x(NiTi)xO19 (x=0, 0.05, 0.1, 0.3, 0.5, 0.7, and 0.9) were synthesized by the solvothermal method. X-ray diffraction (XRD) analysis reveals that the samples are of pure-phase with the space group of p63/mmc. As the Ni-Ti substitution level increases from x=0 to 0.9, the results of field-emission scanning electronic microscopy indicate that the particles are agglomerated and the mean particle size decreases. With the increase in substitution concentration x, the saturation magnetization increases first, and then declines slowly, whereas the coercivity decreases gradually. The variation of magnetic properties can be explained by the effects of Ni-Ti substitution. The results above indicate that our samples have positive effects on high density perpendicular recording. [ABSTRACT FROM AUTHOR]

Ni0.5Zn0.5Fe2O4 particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show super paramagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure. [ABSTRACT FROM AUTHOR]