Mai Lu

Structure and magnetic properties of Zn–Ti-substituted Ba-ferrite particles for magnetic recording

Abstract The formation process of Zn–Ti-doped Ba-ferrite particles was investigated by the X-ray diffraction technique, transmission electron microscope and magnetic measurements. The effects of heating temperature T h and the Zn–Ti substitution x on the microstructure and magnetic properties of BaFe 12−2 x Zn x Ti x O 19 particles with x =0.10–0.80 were studied. The temperature dependence of magnetic properties of these particles was measured.

The temperature dependence of magnetic properties of Zn–Ti substituted Ba-ferrite particles for magnetic recording

Abstract It was shown that the morphological and magnetic properties of Zn–Ti doped Ba-ferrite particles are suitable for magnetic recording. In order to clarify the temperature dependence of the magnetic properties of these particles, BaFe10.8−2xZnxTixO19 particles with the nominal composition x=0.0–0.50 were prepared by synthesis from salt melts. The saturation magnetization Ms, magnetic anisotropy field HA and magnetocrystalline anisotropy constant K1 of the above-mentioned particle assemblies were estimated by using the law of approach to saturation of polycrystalline ferrite, and the Curie temperature Tc was determined by the thermodynamic relation. With an increasing x, the Tc decreased, while the lattice parameters a, c and M s have an unnoticeable maximum at x=0.20. The Hc(T) curves of samples with different x show that all particles have positive temperature coefficient in the vicinity of room temperature, which decreases with increasing x. The Ms(T), H A (T) and K 1 (T) were determined and discussed.

On the Main Mode of Trapezoidal-Groove Guide By Finite Element Method

In this paper, the propagation properties such as the dispersion characteristics, cut-off wavelength, guide wavelength and field distribution for the main mode of trapezoidal-groove guide are analysed by using the finite element method. The dispersion is very low, and the field distribution in a trapezoidal-groove guide is similar to that of rectangular one. The results have important values in design, manufacture, and application of groove guides.

Analysis for dispersion characteristics of trapezoidal-groove waveguide

In this paper, the dispersion characteristics of the main mode for the trapezoidal-groove guides are analysed by using the approach of equivalent network with transverse resonance. The relationship curves between guide wavelength, phase constant and guide dimensions, frequency are obtained. The characteristics have important values in design, manufacture and application of groove guides.

On the Dominant Mode in Closed Trapezoidal-Groove Guide by Finite Element Method

The structure of closed trapezoidal-groove guide is similiar to that of open one, but it can be used to prevent energy from leaking out of the guide. In this paper, the propagation characteristics of dominant mode in closed trapezoidal-groove guide are analysed by using finite element method and the results are discussed.

Magnetic Properties of Co–Sn Substituted Barium-Ferrite Particles for Magnetic Recording

In order to improve the margin for operating temperature changes and to achieve high recording performance, Co-Sn substituted Ba-ferrite particles were investigated. It was found that BaFe12-xCoxSnxO19 particles with x = 1.10 to 1.40 not only have a coercivity suitable for magnetic recording, but also have a very low temperature coefficient of coercivity Delta H-c/Delta T in the temperature range from 0 to 60 degrees C.

Analysis for dispersion characteristics of elliptic- and parabolic-groove waveguides

In this paper, the dispersion characteristics of elliptic-and parabolic-groove guides are analysed by using the equivalent network method with rectangular step approximation. The results have important values in the studying of the transmission characteristics of curvilineal-groove guides as well as its manufacture and application.

On the Computation of Local-Demagnetization Tensor for Nonellipsoidal Ferrites

The distribution of the magnetization in ferrite devices is nonuniform due to their nonellipsoidal shapes. In this paper, the local-demagnetization tensor of magnetized nonellipsoidal ferrite is proposed and calculated. By analysing the distribution of the tensor elements, the distribution of the demagnetizing field can be obtained. The method is simple yet accurate. It can be used to calculate the nonuniform magnetizing distribution in ferrite devices as well as optimize the ferrite devices in the CAD of MMIC.

Finite Element Analysis of the Field Patterns in Elliptical Waveguide

In this paper, finite element method is first used to discuss the field patterns in a hollow perfectly conducting pipe with elliptical cross section. The electrical field lines of the dominant TE mode as well as the magnetic field lines of the lowest TM mode are presented. The results are the same with literatures, and also give a correction to the field pattern of the lowest TM mode in elliptical waveguide.

On the electric field lines of the dominant mode in V-groove guide by finite element method

The electric field lines of the dominant mode in a closed V-groove guide as well as an open one are analysed by the finite element method. The electric field lines are perpendicular to the parallel plate regions. The V-groove guide cannot be regarded as low-loss waveguiding structure.