Bulletin of the Russian Academy of Sciences: Physics最新文献

The data are shown on magnetic properties and peculiarities of nonlinear current-voltage characteristics of manganites with substitution of (({text{Fe}}_{{{text{0}}{text{.5}}}}^{{{text{3 + }}}}{text{Sc}}_{{{text{0}}{text{.5}}}}^{{{text{3 + }}}})), (({text{Ni}}_{{0.5}}^{{2 + }}{text{Ge}}_{{0.5}}^{{4 + }})), (({text{Zn}}_{{0.5}}^{{2 + }}{text{Ge}}_{{0.5}}^{{4 + }})), (({text{Mg}}_{{{text{0}}{text{.5}}}}^{{{text{2 + }}}}{text{Ge}}_{{{text{0}}{text{.5}}}}^{{{text{4 + }}}})) ions pairs for manganese in La–Sr system. The samples containing (Fe,Sc), (Ni,Ge) and (Zn,Ge) have S-shaped sections of negative differential resistance, and (Mg,Ge)-substituted manganite exhibits the property of voltage stabilization.

The optical effects of dichroism, static light scattering, and light attenuation under the action of a magnetic field in magnetic fluids with an average particle size of 6.7 and 13.7 nm were studied. Significant differences were found both in the magnitude of the effects and in their spectral behavior. They can be due to the formation of aggregates in the sample with larger particles, which significantly change the optical properties of the system. The formation of aggregates under the action of the field was confirmed by dynamic light scattering.

Electroconvection in kerosene-based magnetic fluids was experimentally studied using the method of dynamic light scattering. A decrease in the relaxation time of the autocorrelation function was discovered at various voltages and interelectrode distances. Based on experimental data, the dependences of the maximum velocity of chaotic electroconvective flows on the voltage on the electrodes and the distance between them were determined.

The authors study the dependence of the static magnetic response of multi-core particles on the number of grains. The magnetization of multi-core particles consisting of grains in the nodes of a cubic lattice is determined via Monte Carlo computer modeling and theoretical calculations. It is established that the magnetization of multi-core particles is sensitive to the number of grains and does not exceed the value predicted within the single-particle Langevin model. The best agreement between the results from theoretical calculations and computer modeling is obtained for multi-core particles consisting of more than 100 grains.

Silicone-based elastomer containing Nd–Fe–B-alloy particles garnished with a small portion of nickel grains has been studied for the capability to conduct alternating current. The observations suggest that the presence of nickel expands the variation range of the conductivity and magnetocapacitance in external magnetic fields. In addition, the composite demonstrates the memory of primary magnetizing manifesting itself as certain specific features of the hysteresis loops depending on the polarity of the external magnetic field.

The frequency of vapor bubble formation and heat transfer when boiling a magnetic fluid in a homogeneous alternating horizontal magnetic field are studied experimentally. Bubbles form on a single center of vapor formation. The induction current in the coil through which the vapor bubbles move is used to measure the frequency of vapor bubble formation. It is found that the specific heat flux and the frequency of vapor bubble formation depend strongly on the frequency of the magnetic field. Results testify to the possibility of effective non-contact control over the boiling of a magnetic fluid, which could have practical applications.

A model medium of micrometer-sized magnetite particles and metal balls with a diameter of 1 mm in a viscous medium (glycerol) was studied. The processes of organization of this system in an increasing external magnetic field were considered. The effect of shear vibrations on the processes of structure formation in the systems under study was also examined. The data obtained can serve as a basis for modeling the dynamics of disperse systems and expanding the understanding of their behavior and organization in magnetic fields and under mechanical influences.

The rise of an air bubble enclosed in a magnetic fluid shell inside an external homogeneous magnetic field directed horizontally is investigated experimentally. It is shown that the magnetic field acting on the magnetic fluid shell alters the shape of the bubble, which is reflected in the quantitative characteristics of rising. Oscillations in the shape of the air bubble are observed as it rises. Results demonstrate the possibility of controlling small volumes of gas that can have practical applications.

Solidification of a magnetic suspension in the presence of a magnetic field can produce a ferrocomposite characterized by an orientation texture along the easy magnetization axes of nanoparticles. The characteristics of this texture were calculated taking into account the interparticle magnetic–dipole interaction within the framework of a modified mean field theory. Theoretical predictions were confirmed by Monte Carlo computer simulation data.

The shape the free surface of a magnetic fluid takes in an external homogeneous magnetic field near solid magnetic bodies is investigated experimentally. The shape of the surface of a magnetic fluid in the vicinity of bodies of different basic geometry (cylinder, ball, and plate) is studied. The pattern of the magnetic fluid surface under the influence of a stationary and alternating magnetic field is considered. It is shown that the shape of the surface depends strongly on the volume of the magnetic fluid, the geometry of the magnetic body, and the magnitude of the magnetic field. Results testify to the possibility of controlling the shape of the free surface of a magnetic fluid, which could find practical application.