Stability of magnetic domains in an amorphous metal wire

Dimensions and energy of domains in the core of an amorphous metal wire are estimated in the work. Influence of the external magnetic field strength and coercive force on the dimensions of a stable domain is investigated. It is demonstrated that the highest stability to an external magnetic field and the least energy have domains comprising cylinder and cone-shaped domain tops and domains with zigzag domain tops. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 83–91, January, 2009.     

Transition from the antiferromagnetic to a nonmagnetic state in FeBO3 under high pressure

A ⁵⁷FeBO₃ single crystal is studied by the nuclear forward scattering (NFS) method. The NFS time spectra from ⁵⁷Fe nuclei are recorded at room temperature under high pressures up to 50 GPa in a diamond anvil cell. In the pressure interval 0<p<44 GPa, the magnetic field H ^Fe at the ⁵⁷Fe nuclei is found to increase nonlinearly, reaching a maximum value of 48.1 T at p=44 GPa. As the pressure increases further and reaches the point p=46 GPa, the field H ^Fe abruptly drops to zero, indicating that a transition from the antiferromagnetic to a non-magnetic state occurs in the crystal. In the pressure interval 0<p<46 GPa, the magnetic moments of the iron ions lie in the (111) basal plane of the crystal. Several possible mechanisms of magnetic collapse are discussed.     

A numerical scheme for the Green–Naghdi model

In this paper a hybrid numerical method using a Godunov type scheme is proposed to solve the Green–Naghdi model describing dispersive “shallow water” waves. The corresponding equations are rewritten in terms of new variables adapted for numerical studies. In particular, the numerical scheme preserves the dynamics of solitary waves. Some numerical results are shown and compared to exact and/or experimental ones in different and significant configurations. A dam-break problem and an impact problem where a liquid cylinder is falling to a rigid wall are solved numerically. This last configuration is also compared with experiments leading to a good qualitative agreement.     

The role of the electron tunneling effect in the coagulation kinetics of polydisperse metal nanocolloids

The energy of pair interactions between metal nanoparticles of different sizes is shown to be able to increase upon coagulation due to the additional electrostatic effect resulting from mutual heteropolar charging of the particles. The tunnel electron transfer occurring upon the collisions between particles of different sizes may be the reason for the charging. The transfer is caused by the dependence of the electron work function on the particle size. The electron transfer through the interparticle gap equalizes the Fermi levels in particles of different sizes and is associated with this dependence. Using the example of bimodal silver nanocolloids, it is shown that mutual heteropolar charging of particles with different sizes may accelerate the coagulation of polydisperse colloidal systems by an order of magnitude or more as compared with monodisperse systems, in which this effect is absent.     

Resonant Equations with Classical Orthogonal Polynomials. II

Ukrainian Mathematical Journal - We study some resonant equations related to the classical orthogonal polynomials on infinite intervals, i.e., the Hermite and the Laguerre orthogonal polynomials,...     

New Constraints on the Axion–Electron Coupling Constant for Solar Axions

JETP Letters - The formation of a single-cycle light bullet during the propagation of a mid-infrared femtosecond laser pulse with an arbitrary initial ellipticity of the light field polarization in...     

Testing coeffcients of AR and bilinear time series models by a graphical approach

AR and bilinear time series models are expressed as time series chain graphical models, based on which, it is shown that the coefficients of AR and bilinear models are the conditional correlation coefficients conditioned on the other components of the time series. Then a graphically based procedure is proposed to test the significance of the coeffcients of AR and bilinear time series. Simulations show that our procedure performs well both in sizes and powers.     

Dispersive Nonlinear Waves in Two-Layer Flows with Free Surface. I. Model Derivation and General Properties

In this paper we derive an approximate multi-dimensional model of dispersive waves propagating in a two-layer fluid with free surface. This model is a "two-layer" generalization of the Green–Naghdi model. Our derivation is based on Hamilton's principle. From the Lagrangian for the full-water problem we obtain an approximate Lagrangian with accuracy O (ɛ²) , where ɛ is the small parameter representing the ratio of a typical vertical scale to a typical horizontal scale. This approach allows us to derive governing equations in a compact and symmetric form. Important properties of the model are revealed. In particular, we introduce the notion of generalized vorticity and derive analogues of integrals of motion, such as Bernoulli integrals, which are well known in ideal Fluid Mechanics. Conservation laws for the total momentum and total energy are also obtained.     

Magnetooptic setup for investigating the dynamic properties of domain walls in thin ferromagnetic films

A magnetooptic Kerr setup is designed for investigating the dynamic properties of domain walls in thin ferromagnetic films subjected to an external magnetic field in the temperature range 20–150°C. With this setup, the method of interrupted magnetization is implemented and the magnetic (domain) structure is visualized based on the meridional Kerr effect. The domain structure is displayed on a PC monitor using a Nikon DXM 1200 high-resolution digital video camera. A dedicated software makes it possible to automatize measurements and data processing.     

Magnetoimpedance effect in FeCoMoSiB amorphous sheets

The magnetoimpedance effect in sheets made of Fe₄Co₆₇Mo_1.5Si_16.5B₁₁ amorphous metallic alloy is studied in relation to the mutual orientations of the sheet axis, permanent magnetic field, and variable electrical current. Also, the effective permeability is studied as a function of the mutual orientations of the sheet axis, permanent magnetic field, and rf magnetic field. Under certain orientations of the rf magnetic field and rf electrical current relative to the sheet axis, experimental dependences of the magnetoimpedance effect and effective permeability on the permanent magnetic field are found to correlate qualitatively. The experimental data are explained in terms of domain reconfiguration in the alloys.