Concentration Of Magnetic Phase Research Articles

Certain Laws of Irreversible Change in the Magnetization of Polycrystalline Ferromagnets

The validity of the Rayleigh law for the return curves which begin in fields whose strength is smaller than the relaxation coercive force of the material is justified on the basis of an analysis of displacements of domain walls. Expressions for the dependence of the Rayleigh coefficient on the input magnetization are obtained from the statistical theory of the magnetic phase concentration. The theoretical expressions obtained are compared with experimental data. The results of the study can be used for optimizing the magnetic testing methods.

Magnetization processes of small -Fe2O3 particles in non-magnetic matrix

The magnetization processes of small (350 Å) and nearly spherical particles of -Fe2O3 were studied at room temperature using the initial, hysteresis and remanence magnetization curves. The effective interparticle interactions were estimated for a number of virgin and alternating current demagnetized samples of -Fe2O3-SiO2 mixtures with different magnetic phase concentrations. A non-monotonous dependence of the interactions on the magnetic phase concentration was observed. It was related to the changes in the domain state of some of the particles from the single-domain to the multi-domain.

Transverse elastic-wave absorption due to reversible rotation in a triaxial magnetic material

Calculations have been performed on the energy absorption related to rotation of the spontaneous-magnetization vectors due to external shearing sign-varying stresses applied to a multidomain magnetic material, where allowance is made for the magnetic-phase concentrations. The perturbation solution for a system of six equations for the rotational moments is found together with the wave equation to derive the deviations of the magnetization vectors from the easy directions in the stress wave field. The absorption coefficients and internal friction have been derived, together with the defect of the shearing modulus, including the frequency dependence, which are determined via the magnetic, magnetoelastic and elastic constants of the crystal in relation to the orientation of the X′ and Y′ axes of the tensor for the stresses σx′y′ with respect to the 〈100〉 easy axes. When the domain boundaries are fixed, the main contribution to this type of absorption in a ferromagnetic arises from the micro-eddy currents, while in a ferrite, it is due to the spin viscosity and the radiational friction.

Yield stress of a magnetic fluid in a magnetic field

The yield stressτ0 of a magnetic fluid in a plane channel and the shape of the chains restraining the motion of the fluid are determined. The equilibrium problem for a magnetic fluid in a plane channel in the presence of an external magnetic field perpendicular to the plane of the channel and a pressure difference between the channel ends is solved within the framework of the structured fluid model. It is shown that equilibrium is possible only when the pressure difference does not exceed a certain limit Δpcr at which the shear stress on the channel wall has a maximum. In weak fields Δpcr and the correspondingτ0 depend quadratically on the field and in strong fields tend to saturation. The phenomenological parameters of the model are estimated for the case in which the microstructure is a system of chains of magnetic particles. The results obtained are found to be in qualitative agreement with the experimentally observed dependence of Δpcr andτ0 on the field and the magnetic phase concentration.

Effect of isotropic surface films on the distribution of magnetic-phase concentrations in transformer steel with ribbed texture

1. Isotropie surface films which produce tensile stresses in their substrates (cold-rolled transformer steel) increase the concentration of the magnetic phase, the vector Js of which is in the rolling direction, while films producing compressional stresses reduce this concentration. 2. For films which are not too thick, the dependence of the ratio of magnetic-phase concentrations on the thickness of the surface film is exponential.