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21.
In calculations using the local spin density approximation, a new group of half-metallic ferromagnets is predicted. This group comprises double perovskites Sr2FeSnO6, Sr2FeTiO6, and Sr2 FeZrO6—systems with one type of magnetic ions that can be obtained by diluting the magnetic sublattice of SrFeO3 with ions of nonmagnetic pn and d0 metals. 相似文献
22.
23.
E. N. Kozhevnikov 《Crystallography Reports》2005,50(5):843-848
The spatially periodic structure arising in a homeotropic nematic-liquid-crystal (NLC) layer in low-frequency Couette flow is described theoretically. The analysis of this phenomenon is based on the hydrodynamic equations for NLCs, from which a self-consistent system of equations is selected for perturbations of hydrodynamic variables: the steady-state angle of the molecule rotation, the liquid flow, and the velocity of oscillating vortex flows. The formation of the periodic structure is explained by the phase delay of the velocities of the vortex oscillating flows forming in the deformed structure with respect to the shear velocity in the Couette flow. It is shown that at low frequencies this difference in the velocities is caused by the orientational waves near the layer boundaries. In the case of fixed orientation of molecules at the boundaries, the dependence of the threshold shear amplitude on the frequency and layer thickness is given by the relation uth ~ (ωh2)?1/4. The influence of the conditions for the molecule orientation at the layer boundaries on the above phenomenon is analyzed. 相似文献
24.
25.
V. E. Tarabanko V. N. Sidelnikov I. V. Kozhevnikov 《Reaction Kinetics and Catalysis Letters》1982,21(1-2):109-114
It has been established that in the oxidation of diethyl sulfide by18O2 in CH3C16O2H–H2
16O solution at 369 K catalyzed by heteropoly acids, sulfoxide and sulfone with 44–54%18O enrichment are formed. The process is accompanied by isotope exchange of molecular oxygen.
, 18O2 CH3C16O2H–H2 16O 369 18O 44–54%, .相似文献
26.
The structure of a planar nematic liquid crystal in an oscillating Couette flow beyond the stability threshold 总被引:1,自引:0,他引:1
E. N. Kozhevnikov 《Acoustical Physics》2008,54(1):25-31
The deformation of a nematic liquid crystal with a planar molecule alignment under the effect of an oscillating Couette flow is theoretically described. The case of external action with amplitudes exceeding the instability threshold of the initial crystal structure is considered. The effect is analyzed by the perturbation method on the basis of the nonlinear equations of nematodynamics. The type and magnitude of the NLC structure distortions are determined as functions of the frequency and amplitude of shear. 相似文献
27.
28.
The optical effect in a liquid crystal cell containing a homeotropic layer of nematic liquid crystal (NLC) is analyzed. An
NLC layer, located between crossed polaroids and opaque in the absence of external effect, is cleared after irradiation by
an ultrasonic beam with a sharp spatial boundary. This enlightenment is suggested to be caused by the reorientation of crystal
molecules in the acoustic flows that arise under the binary effect of the layer compression in the irradiated region and the
viscous waves propagating from the layer boundaries. The flows were calculated taking into account the stress caused by the
velocity convection and crystal structure relaxation. An expression is derived for the cell transparency, and the relative
role of the convection and relaxation processes in the effect is determined. 相似文献
29.
S.V. Kozhevnikov A. RühmF. Ott N.K. PleshanovJ. Major 《Physica B: Condensed Matter》2011,406(12):2463-2466
A neutron waveguide is a three-layer structure in which a guiding layer with low optical potential is placed between two cladding layers with high optical potential. Under proper operation conditions, the neutron density is resonantly enhanced inside the guiding layer. In our experimental scheme, the neutron beam enters through the surface of the top layer at glancing angle and goes out from the edge of the guiding layer, with an angular distribution corresponding to Fraunhofer diffraction from a narrow slit. The incident neutron beam is relatively wide (0.1 mm) and highly collimated (0.01°). The outgoing sub-micron beam is extremely narrow at the outlet (0.1 μm) and more divergent (0.1°). So far only the production of unpolarized sub-micron neutron beams has been reported. Here we present first experiments on polarized sub-micron neutron beams. For these studies a polarized incident beam was used and two types of magnetic waveguides were investigated: a polarizing magnetic waveguide Fe(20 nm)/Cu(140 nm)/Fe(50 nm)//glass and a non-polarizing magnetic waveguide Py(10 nm)/Al(140 nm)/Py(50 nm)//glass (Py is permalloy). The waveguide samples were characterized by polarized neutron reflectometry. 相似文献
30.