Specific features in precession dynamics of magnetization of a uniaxial magnetic film

The precession dynamics of the magnetization of a film with in-plane uniaxial anisotropy in the case of its biasing along the hard magnetization axis has been analyzed by numerically solving the Landau-Lifshitz equations. It has been revealed that the ferromagnetic resonance spectrum near the magnetic anisotropy field exhibits an additional peak, which is associated with the angular bistability due to the presence of two symmetric angular equilibrium positions. The trajectories of precession motion during biasing along the hard magnetization axis differ substantially from the trajectories corresponding to the biasing along the easy axis.     

Experimental small-angle X-ray scattering investigation of initial stages of the spinodal decomposition in model sodium silicate glasses

The kinetics of the initial stages of the spinodal decomposition in model glasses of the Na₂O-SiO₂ system has been investigated in situ. It has been demonstrated that there is a quantitative agreement of the experimental results obtained in the framework of the Stephenson theory with the basic principles of modern theories and the data on direct determination of the viscosity, mobility, and diffusion. It has been found that the spatial-temporal evolution of the heterogeneous structure has a multistage character during spinodal decomposition. The characteristic size of the phase regions at each stage varies with time according to the power law. The sequence of stages and the values of exponents for the spinodal decomposition are as follows: 1/20, 1/4, 1/2, and 1/3.     

Sol-Gel Synthesis and Optical Studies of Rare Earth and Transition Metal Ions Doped Nanocrystalline Aluminum and Yttrium Oxides

The paper reviews the studies of sol-gel produced nanocrystalline -Al₂O₃ and cubic Y₂O₃ doped with RE³⁺ and TM³⁺ ions. The effects of spatial confinement (on nanometer scale) in optical properties of sol-gel produced insulating nanocrystalline oxide materials doped with rare earth and transition metal ions are discussed. The experimental studies showed that in insulators these effects are mostly connected with the changes in the vibrational spectrum and the increased role of the surface in nanocrystals. The transformations between the crystalline forms of Al₂O₃ and the properties of doped corundum ceramics are studied. The methods of sol-gel synthesis of highly dispersed nanocrystalline -Al₂O₃ and cubic Y₂O₃ doped with RE³⁺ and TM³⁺ ions in wide range of concentrations are described. It is shown that optical techniques are useful for characterization of sol-gel produced materials.     

Structures of stiff macromolecules of finite chain length near the coil‐globule transition: A Monte Carlo simulation

Using a coarse‐grained model of a semiflexible macromolecule, the equilibrium shapes of the chain have been studied varying both the temperature and the chain stiffness. We have applied Monte Carlo techniques using the bond fluctuation model for a chain length of N = 80 effective monomers, and two different types of interactions: a potential depending on the angle between successive bonds along the chain to control the chain stiffness, and an attractive interaction between non‐bonded effective monomers to model variable solvent quality. In a diagram of states where chain stiffness and inverse temperature are used as variables, we find regions where the chain exists as coil, as spherical globule, and as toroidal globule, respectively. Some of these regions are not limited by sharply defined boundaries, but rather wide two‐state coexistence regions occur in between them, where also intermediate metastable structures (such as rods and disks) occur. Recording histograms of energy, orientational order parameters, etc., which exhibit a two‐peak structure in the two‐state coexistence regions, we perform a subensemble analysis of the individual structures corresponding to these peaks.     

Ferromagnetic resonance in metal films with angular dispersion of magnetic anisotropy

The specific features of the ferromagnetic resonance spectra of metal magnetic films due to the cubic crystalline anisotropy and induced uniaxial magnetic anisotropy have been studied using the statistical model of noninteracting blocks. It has been demonstrated that the inclusion of the angular dispersion of the fields of these magnetic anisotropies leads to a shift, asymmetry, and broadening of the integral resonance curve and to characteristic angular dependences of the resonance field and the resonance line width.     

Small-angle X-ray scattering study of the structure of glassy nanoporous matrices

The structure of high-silica glassy nanoporous matrices prepared from two-phase glasses has been investigated using the small-angle X-ray scattering technique. Parameters of materials, such as the density, porosity, specific surface area, average nanopore radius, average radius of scattering particles filling the pore space, and their fractal dimensions, have been determined. The dependence of the obtained structural parameters on the conditions of chemical treatment of glasses has been established. It has been demonstrated that the results obtained are in good agreement with porosimetry and electron microscopy data.     

Destruction of globules of Co- and homopolymer macromolecules in the presence of an amphiphilic substrate

The destruction of a globule in the presence of a dimeric substrate composed of a hydrophilic group OP and a hydrophobic group H with a high affinity to hydrophobic H units of a macromolecule has been studied. Globules of the homopolymer H macromolecule and the macromolecule of the HP copolymer with proteinlike statistics of monomer unit distribution along a chain have been investigated. The destruction of a globule in such systems begins with the transformation of the globule’s shape from spherical to disklike. At high substrate concentrations, the globule of the proteinlike copolymer is completely destroyed; under the same conditions, the homopolymer macromolecule forms a structure composed of two beads having a shape close to that of the oblate ellipsoid that are located symmetrically about a string connecting them.