Academic literature on the topic 'Ferrite Magnetic properties'

Nanocrystalline Ni 1-x Zn x Fe 2 O 4 (0.0 ≤ x ≤ 1.0) spinels are synthesized with a crystallite size range 5–2.2 nm, using different annealing temperatures. The influence of zinc content as well as grain size of ferrite on the ferrite microstructure, therefore on the physical properties of ferrite, are investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), thermal analysis (TG, DTG, DSC) and infrared microscopy (IR). XRD results confirm single phase spinel structure for ferrite with Zn content x = 0.1 whereas second phase appears in higher zinc content ferrites. Thermal analysis shows an endothermic peak at ~ 720°C–750°C reveals the removal of defective surface layer existed on the surface of ferrite grains, which leads to cation redistribution. This is supported by the shift observed in IR bands as a result of the increase in zinc content or calcination temperature. Ferrite with composition Ni 0.7 Zn 0.3 Fe 2 O 4 calcined at 1000°C has the maximum saturation magnetization Ms among various compositions at different calcination temperatures. The Ms and the coercivity Hc of the ferrites nanoparticles are different from their corresponding bulk, which attributes to a defective surface layer, controlling the ultrafine particle behavior.

The magnetic properties of a pure Nickel metal and Nickel-Zinc-Manganese ferrites having the chemical formula Ni0.1(Zn0.4Mn0.6)0.9Fe2O4 were studied. The phase formation and crystal structure was studied by using x-ray diffraction which confirmed the formation of pure single spinel cubic phase with space group (Fd3m) in the ferrite. The samples microstructure was studied with scanning electron microstructure and EDX. The magnetic properties of the ferrite and nickel metal were characterized by using a laboratory setup with a magnetic field in the range from 0-500 G. The ferrite showed perfect soft spinel phase behavior while the nickel sample showed higher magnetic loss and coercivity.

Subject and Purpose. The use of spatially structured ferromagnets is promising for designing materials with unique predetermined electromagnetic properties welcome to the development of magnetically controlled microwave and optical devices. The paper addresses the electromagnetic properties of structured ferrite samples of a different shape (spatial geometry) and is devoted to their research by the method of electron spin resonance (ESR). Methods and methodology. The research into magnetic properties of structured ferrite samples was performed by the ESR method. The measurements of transmission coefficient spectra were carried out inside a rectangular waveguide with an external magnetic field applied. Results. We have experimentally shown that over a range of external magnetic field strengths, the frequency of the ferromagnetic resonance (FMR) of grooved ferrite samples (groove type spatial geometry) increases with the groove depth. The FMR frequency depends also on the groove orientation relative to the long side of the sample. We have shown that as the external static magnetic field approaches the saturation field of the ferrite, the FMR frequency dependence on the external static magnetic field demonstrates "jump-like" behavior. And as the magnetic field exceeds the ferrite saturation field, the FMR frequency dependence on the groove depth gets a monotonic character and rises with the further growth of the field strength. Conclusion. We have shown that the use of structured ferrites as microwave electronics components becomes reasonable at magnetic field strengths exceeding the saturation field of the ferrite. At these fields, such a ferrite offers a monotonically increasing dependence of the resonant frequency on the external magnetic field and on the depth of grooves on the ferrite surface. Structured ferrites are promising in the microwave range as components of controlled filters, polarizers, anisotropic ferrite resonators since they can provide predetermined effective permeability and anisotropy

The sintering of RF plasma synthesized NiZn ferrite nanoparticles was studied. The as-synthesized nanoparticles have been modeled as having a core-shell structure with richer Zn concentration on the surface. Most Zn cations occupy tetrahedral sites typical of zinc ferrites, while some of the Zn cations occupy tetrahedral sites in a (111) oriented surface layer in the form of ZnO. Ni and Fe cations show no evidence of such disorder and their positions are consistent with the bulk spinel structure. This core-shell structure evolves by decomposition of the as-synthesized nanoparticles into Ni-and Zn-rich ferrites followed by the decomposition of the Zn-rich ferrites into ZnO and -Fe2O3 during sintering of the nanoparticles. Within the core region, sintering causes Ni to exit the ferrite structure and be reduced to a metallic form, possibly via a NiO intermediate. The miscibility gap in the pseudo-binary ZnFe2O4/NiFe2O4 system was modeled using equilibrium solution data. Decomposition rates are interpreted considering inter-diffusion kinetics. Sintered nanoparticle compacts showed an evolution of a 4- phase mixture of ferrite + ZnO + -Fe2O3 + Ni with increasing sintering temperature. The average ferrite nanoparticle size is preserved up to very high sintering temperatures. These observations suggest that the ZnO shell contributes to the sintering process by surface diffusion while acting as a barrier to the growth of the ferrite core. Metal edge EXAFS patterns of the sintered compacts confirm that Fe transforms from a single ferrite phase into a mixture of -Fe2O3 and ferrite; ZnO content progressively increases with sintering temperature and elemental Ni evolves from the ferrite with increasing sintering temperature. The saturation magnetization and Curie temperature were observed to decrease as a function of sintering temperature, with an anomaly at the temperature where Ni starts to form. This is explained by Zn diffusing from the core depleting the ferrite and increasing the amount of non-magnetic ZnO in the shell. AC magnetic measurements also vary systematically with the microstructural evolution.