Автоматический выпуск конструкторской документации в PDM-системе

BaFe12O19 powders were prepared by coprecipitation and by glass crystallization. Electron microscopic investigations revealed that the particles of the glass crystallized powder exhibit excellent uniform shapes and narrow size distribution in comparison to the coprecipitated one consisting of irregularly shaped, polycrystalline particles with a broad and inhomogeneous size distribution. The crystallites of the coprecipitated powder particles, however, are smaller (mean diameter D = 0.11 μm) and the size distribution is narrower than that of the particles of the glass crystallized powder with a mean diameter of D = 0.42 μm. The lattice perfection of the particles and the crystallites of both ensembles is quite good. In order to determine the magnetic properties - above all the effective anisotropy field - we used six different methods: transverse susceptibility χt, singular point detection (SPD), ferromagnetic resonance (FMR), torsion pendulum (TP), rotational hysteresis losses (RHL), remanence curves (RC). It has been found that differences in coercivity values HcJ are not dramatic (about ±3%). Effective anisotropy fields Ha measured with “switching” methods (RHL, RC) are smaller than those measured with “stiffness” ones (FMR, TP, SPD, χt), by about 1700 Oe for the coprecipitated powder and about 2500 Oe for the glass crystallized one. The glass crystallized particle assemblies used for the present investigations do not exhibit pure Stoner-Wohlfarth behaviour, because of their relatively large particle diameters. The ratio HcJ/Ha ≈ 0.39 of the coprecipitated powder is relatively near the ideal value of 0.48, although the particles are considerably mechanically aggregated. © 1992

Structural and Magnetic Properties of Ba-ferrite Fine Particles Grown by Glass Crystallization

The dependence of the specific saturation magnetization on the particle size of pure and Co-Ti-substituted Ba-ferrites was interpreted in terms of a nonmagnetic surface layer parallel to the c-planes of 1.3 nm and 0.7 nm, respectively, in thickness. Electron microscope investigations of the particles demonstrate that this effect arises neither from a sufficient fraction of superparamagnetic particles in the ensemble nor from the Co-Ti substitution or from surface defects such as steps and stacking disorder of the building blocks. Extrapolating this surface effect to small sizes yields a critical size, with the particles losing their ferrimagnetic behaviour. This critical size agrees surprisingly well with the volume calculated for the transition of the single domain state to the superparamagnetic one. © 1991 Springer Verlag

Preparation and Characterization of Hexaferrite Powders

A survey is given of the preparation and characterization of hexaferrite powders. Regarding the technical applications of such powders the main emphasis is put on M-type barium ferrite ones. Of the different preparation techniques the glass crystallization method is concluded to be convenient to generate excellent powders for magnetic recording media. Therefore this outstanding method is described in more detail and results about the growth kinetics of M-type particles are presented. The characterization is focused on the chemical and structural as well as magnetic properties of the powder particles

Growth Kinetics and Some Properties of Thick LPE YIG Layers

Three high temperature solutions (HTS) with liquidus temperatures T L = 876°C(1), 980°C(2), and 1005°C (3) were used for the deposition of thick Y 3-uPb uFe 5-tPt tO 12 layers on 20 mm and 50 mm diameter 111 Gd 3Ga 5O 12 substrates and of thin layers on slightly spherically shaped 110 and 211 substrates. The transport resistance δ/D of HTS 1 is larger by a factor 1.8 and the interfacial resistance 1/k by a factor 6.5 compared with those of HTS 3. The kinetic coefficients k st of steps of HTS 1 and those of HTS 2 and HTS 3 differ by about an order of magnitude. Characterization of 111 thick layers is carried out with respect to composition, misfit, magnetic saturation polarization, Curie temperature, and ferromagnetic resonance linewidth. © 1988

Properties of Barium Hexaferrite Powders for Magnetic Recording

Substituted barium hexaferrite powders prepared by the glass crystallization method are investigated geometrically and magnetically. Evaluating a special kind of remanence curves allows the anisotropy field distribution of the powders to be determined. In order to obtain the intrinsic anisotropy field distribution the influence of thermal fluctuations must be separated from the data. The magnetic properties of powders of different composition are discussed. © 1993

Optimization of Flux Composition for Thick YIG Layers

Thick, nominally pure (only lead substituted) Y 3Fe 5O 12 (YIG) films have been grown on gadolinium gallium garnet (GGG) substrates 2 inches in diameter by isothermal dipping method of liquid phase epitaxy from lead-borate melt. If the liquidus temperature of the melt and the supercooling are varied over in a wide range, 1151-1319 K and 10-48 K, respectively, and one examines the supercoolability of the melt, the lattice parameter, Pb content, FMR linewidth and the surface quality of the prepared layer it can be stated that nominally pure YIG layer on GGG substrate 50 mm in diameter can be grown by only one dipping step up to about 80 μm in thickness without surface defects. © 1987 Akadémiai Kiadó

Magnetic Properties of Nanocrystalline Barium Hexaferrite Powders: Anisotropy Field and Interaction Effects

The anisotropy field H a of nanocrystalline barium hexaferrite powders is determined and the influence of interaction between the particles is investigated. The value of H a is found to be extremely high, which may be explained by surface effects. The powders show positive interaction in the superparamagnetic regime (high temperatures) and negative interaction in the magnetic stable regime (low temperatures). © 1993

Structural and Magnetic Properties of BaFe₁₂₋₂ₓCoₓTiₓO₁₉ Powders Prepared by the Glass Crystallization Method

The glass crystallization method is shown to be suitable for preparing BaFe12-2xCox TixO19 powders with a nearly perfect crystallographic structure and a narrow particle size distribution. The dependences of the specific magnetization, the coercivity, and the particle size distribution on both the annealing temperature and the Co-Ti content correlate in a characteristic way. Furthermore, the lattice parameters, the specific surfaces and the thickness of the effective nonmagnetic surface layer were determined. The coercivity of the hexaferrite magnetic tapes is more than 8 × 103 A/m higher than for the corresponding powders