The spatial and temporal evolution of small perturbations of the temperature and electromagnetic field for the simplest geometry, i.e., in a superconducting slab placed in a parallel magnetic field is considered.The obtained solution solution describes an blow-up-type instability in the superconductor sample.It remains localized within the limited area x < L * / 2 with increasing infinitively of time.
Behavior of spin-wave propagation in ferromagnetic medium with non-uniform distribution of magnetic parameters is studied. In particular, the influence of external magnetic field, spin-wave frequency and exchange parameter on behavior of surface spin-wave propagating through inhomogeneity made in form of lens (lens is biaxial ferromagnet placed into uniaxial ferromagnetic medium) is studied.
The effect of pressure on the structural and electronic parameters of zinc-blende aluminum phosphide crystal has been investigated using the large unit cell within the framework of complete neglect of differential overlap and the linear combination of atomic orbital approximation. Cohesive energy, indirect band gap, valence bandwidth, conduction bandwidth, bulk modulus, and valence charge distribution are all obtained. The calculations show a good agreement of lattice constant, cohesive energy, valence bandwidth, and bulk modulus with the experimental data. The calculated band gap is twice the experimental value. This high value of the band gap is expected in Hartree-Fock method. The effect of pressure on the aforementioned properties is investigated. It is found that the indirect band gap, valence bandwidth, bulk modulus and cohesive energy increase with increasing pressure, while the conduction bandwidth decreases. The maximum value of pressure is taken to be 9 GPa, because beyond this value, the phase of AlP transforms from zinc blende phase to nickel arsenic phase.
The temperature-dependent structural changes were investigated by using the X-ray diffraction and the Extended X-ray absorption fine spectroscopy (EXAFS) for layered perovskite manganites La2-2xSr1+2xMn2O7 (x=0.33 and 0.4). The anomalous changes of Mn-O bond length and Jahn-Teller (J-T) distortion of MnO6 octahedron were observed, corresponding to ferromagnetic transition temperature (~ 120 K). Around the temperature of 2D short-range magnetic ordering (~ 235 K), there occurs an anomaly of the Jahn-Teller distortions of MnO6. These results indicate that magnetic properties of perovskite manganites La2-2xSr1+2xMn2O7 depend heavily on their microstructure change. The orbital state occupancy is involved in the observed Mn-O bond change.
Raman spectra of nanocrystals titanium dioxide are discussed and the correlation between the band shape of the allowed A1g Raman mode and the crystals dimensions is discussed. Data on Raman spectra are reconsidered in the frame- work of a modified "hard confinement" model (MHC). The proposed model is based on the idea of using an effective linewidth parameter, which is a function of the effective dimension of the nanostructure, in spite of the intrinsic Raman band linewidth. The comparison with standard hard confinement model reveals better agreement with the experimental results for the MHC model up to 6 nm. Moreover, the analysis permits to improve the knowledge of the phonon dispersion curve as well as the intrinsic Raman bulk parameters. An analytical form of the size-dependent peak-position in nanocrystals, useful for an approximated size estimation, has been explicated. The general structure of the model permits to extended the MHC to other nano-sized materials.
