High frequency manganese-zinc ferrite was prepared by oxide ceramic process. The microstructure of representative samples was analyzed by scanning electron microscope (SEM). In addition, the resistivity (ρ) of samples was tested by YY2812 LCR meter and the magnetic properties were obtained by SY-8232 B-H Analyzer. In combination with the microstructure analysis of material, the effects of SnO 2 additive in MnZn ferrite were investigated, especially on initial permeability (µ i ), resistivity (ρ), hysteresis loss (P h ), eddy current loss (P e ) and residual loss (P r ). The results show that the amount of SnO 2 additive has an obvious influence on the microstructure and electromagnetic properties of the proposed material, such as µ i , ρ, P h , P e and P r . There is an optimum content of SnO 2 which is 0.1% to ensure finer microstructure and lower loss at the frequency of 1MHz.

M-type Ba-hexaferrite (BaM) thin films with two different structures (single layered and double layered) were deposited on (001) Al2O3 substrates by RF magnetron sputtering. The changes in microstructural and magnetic properties of the films corresponding to different layer structures and substrate temperatures (Ts) were investigated. Experimental results indicated that for the single layered films deposited directly on substrates at Ts = 300 °C and Ts = 500 °C, most of the grains are acicular type grains with their c-axis in-plane and/or randomly oriented. However, in the double layered film with first interfacial layer deposited at Ts = 300 °C and second layer deposited at Ts = 500 °C, good crystallographic characteristics and excellent perpendicular c-axis orientation were obtained. The c-axis dispersion angle (Δθc) decreased to 0.49°, while the squareness ratio and coercivity of the out-of-plane respectively increased to 0.85 and 4.67 kOe in the double layered film. The mechanism for improving perpendicular c-axis orientation with the interfacial BaM layer was attributed to an increase in the perpendicularly oriented nucleation sites and the release of the stress that comes from the film-substrate interface.

In this paper, several new main compositions are presented with Mn2+ substituted by Ti4+ and Co2+ in Manganese-zinc ferrites in consideration of the strong influence of Ti4+ and Co2+ on thermal stability by different mechanisms. Moreover, the effects of these substitutions on such parameters as permeability, electrical resistivity, density, and power loss are analyzed. The experimental results show that the proper substitution of Ti4+ or Co2+ in manganese-zinc ferrites can increase the thermal stability remarkably. Furthermore, the effects of composition of Ti4+ and Co2+substitutions have interactive process, especially when Manganese-zinc ferrites with high thermal stability in 20°C~140°C are achieved when the substitution of Ti4+ is 0.10mol%and Co2+ is 0.05mol%.

The Sr hexaferrites with chemical formula Sr0.4La0.3Ca0.3Fe11.85-xGaxCo0.15O19 (x = 0.0 — 1.4) were manufactured by traditional ceramic method. The affect of Ga substitution on static magnetic properties and micromorphology of M-type Sr (SrM) hexaferrites have been presented in detail. In accordance with the experiment results, as Ga-substituted content x rises up from 0.0 to 1.4, all SrM hexaferrite samples are magnetoplumbite hexagonal structure. The difference between radius of Fe3+ and Ga3+ ions leads to the decrease of lattice constants. As the amount of Ga substitution x increases from 0.0 to 1.4, the 4πMs and 4πMr presents a trend of increasing, but the Hc shows the opposite trend. K1 and Ha of all samples are higher than 2.5×105 J/m3 and 21 kOe respectively, which manifests all samples possess the strong uniaxial anisotropy. The materials discussed in this paper possess huge potential in the application of high frequency self-biased microwave devices.

The effects of NiO on density and mechanic strength of Mn-Zn ferrite used for inertial gyroscope were investigated by measurements of crystal lattice constant, Vickers hardness, bending strength. To investigate this further, powder of Mn-Zn ferrite was characterized by x-ray diffraction (XRD) and the fracture surface of Mn-Zn ferrite was checked by scanning electronic microscope (SEM). The investigation revealed that the substitution of Ni2+ modified crystal lattice constant and crystal grain size so that it caused crystal lattice constant of Mn-Zn ferrite to decline and crystal grain size to decrease, therefore it was useful to improve density and mechanic strength of Mn-Zn ferrite by this way. The results show that proper addition of NiO can bring higher density and more perfect mechanic strength of Mn-Zn ferrite used for inertial gyroscope.