14 research outputs found

    Evidence for reversible control of magnetization in a ferromagnetic material via spin-orbit magnetic field

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    Conventional computer electronics creates a dichotomy between how information is processed and how it is stored. Silicon chips process information by controlling the flow of charge through a network of logic gates. This information is then stored, most commonly, by encoding it in the orientation of magnetic domains of a computer hard disk. The key obstacle to a more intimate integration of magnetic materials into devices and circuit processing information is a lack of efficient means to control their magnetization. This is usually achieved with an external magnetic field or by the injection of spin-polarized currents. The latter can be significantly enhanced in materials whose ferromagnetic properties are mediated by charge carriers. Among these materials, conductors lacking spatial inversion symmetry couple charge currents to spin by intrinsic spin-orbit (SO) interactions, inducing nonequilibrium spin polarization tunable by local electric fields. Here we show that magnetization of a ferromagnet can be reversibly manipulated by the SO-induced polarization of carrier spins generated by unpolarized currents. Specifically, we demonstrate domain rotation and hysteretic switching of magnetization between two orthogonal easy axes in a model ferromagnetic semiconductor.Comment: 10 pages including supplemental materia

    Optimal triple configurations of stationary shocks

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    The triple configurations of stationary shock waves with negative slope angle of the reflected shock to the velocity vector of the supersonic stream before the triple point (ā€œinverseā€ triple configurations) are considered. ā€œInverseā€ configurations with maximum relations of flow parameters at the slipstream after triple point are determined. Extreme relations of the flow parameters downstream the ā€œinverseā€ configurations are compared with the parameters achieved on the whole set of the triple-shock configurations that appear in supersonic streams of the inviscid perfect gas

    Optimal regular reflection of shock and blast waves

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    The regular reflection of an oblique steady shock in supersonic gas flow is considered. The static pressure extremum conditions after the point of reflection of the shock with fixed strength depending on oncoming flow Mach number are determined analytically. The obtained results are applied to solution of the mechanically equivalent problem of the reflection of a propagating shock from an inclined surface. Non-monotonic variation of the mechanical loads on the obstacle with respect to its inclination angle is shown; the obstacle slope angles that correspond to pressure minima downwards of the unsteady shock reflection point are determined analytically

    Optimal triple configurations of stationary shocks

    No full text
    The triple configurations of stationary shock waves with negative slope angle of the reflected shock to the velocity vector of the supersonic stream before the triple point (ā€œinverseā€ triple configurations) are considered. ā€œInverseā€ configurations with maximum relations of flow parameters at the slipstream after triple point are determined. Extreme relations of the flow parameters downstream the ā€œinverseā€ configurations are compared with the parameters achieved on the whole set of the triple-shock configurations that appear in supersonic streams of the inviscid perfect gas

    Optimal regular reflection of shock and blast waves

    No full text
    The regular reflection of an oblique steady shock in supersonic gas flow is considered. The static pressure extremum conditions after the point of reflection of the shock with fixed strength depending on oncoming flow Mach number are determined analytically. The obtained results are applied to solution of the mechanically equivalent problem of the reflection of a propagating shock from an inclined surface. Non-monotonic variation of the mechanical loads on the obstacle with respect to its inclination angle is shown; the obstacle slope angles that correspond to pressure minima downwards of the unsteady shock reflection point are determined analytically

    Graphene oxide hydration and solvation : an in situ neutron reflectivity study

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    Graphene oxide membranes were recently suggested for applications in separation of ethanol from water using a vapor permeation method. Using isotope contrast, neutron reflectivity was applied to evaluate the amounts of solvents intercalated into a membrane from pure and binary vapors and to evaluate the selectivity of the membrane permeation. Particularly, the effect of D2O, ethanol and D2Oā€“ethanol vapours on graphene oxide (GO) thin films (25 nm) was studied. The interlayer spacing of GO and the amount of intercalated solvents were evaluated simultaneously as a function of vapour exposure duration. The significant difference in neutron scattering length density between D2O and ethanol allows distinguishing insertion of each component of the binary mixture into the GO structure. The amount of intercalated solvent at saturation corresponds to 1.4 molecules per formula unit for pure D2O (1.4 monolayers) and 0.45 molecules per formula unit (one monolayer) for pure ethanol. This amount is in addition to H2O absorbed at ambient humidity. Exposure of the GO film to ethanolā€“D2O vapours results in intercalation of GO with both solvents even for high ethanol concentration. A mixed D2Oā€“ethanol layer inserted into the GO structure is water enriched compared to the composition of vapours due to slower ethanol diffusion into GO interlayer

    Cation Size and Anion Anisotropy in Structural Chemistry of Metal Borohydrides. The Peculiar Pressure Evolution of RbBH4

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    The pressure evolution of RbBH4 has been characterized by synchrotron powder X-ray diffraction and Raman spectroscopy up to 23 GPa. Diffraction experiments at ambient temperature reveal three phase transitions, at 3.0, 10.4, and 18 GPa (at 2.6, 7.8, and ~20 GPa from Raman data), at which the space group symmetry changes in the order Fm-3m(Z=4) ā†’ P4/nmm(2) ā†’ C222(2) ā†’ I-42m(4). Crystal structures and equations of state are reported for all four phases. The three high-pressure structure types are new in the crystal chemistry of borohydrides. RbBH4 polymorphs reveal high coordination numbers (CNs) for cation and anion sites, increasing with pressure from 6 to 8, via an intermediate 4 + 4 coordination. Different arrangements of the tetrahedral BH4 group in the Rb environment define the crystal symmetries of the RbBH4 polymorphs. The structural evolution in the MBH4 series is determined by the cation's size, as it differs drastically for M = Li (CNs = 4, 6), Na (CN = 6), and Rb. The only structure common to the whole MBH4 family is the cubic one. Its bulk modulus linearly decreases as the ionic radius of M increases, indicating that the compressibility of the material is mainly determined by the repulsive BH4Ā·Ā·Ā·BH4 interactions

    Electrical control of ferromagnetic state

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    We report experiments where magnetization in GaMnAs ferromagnetic semiconductor is manipulated via strain or electric current. In both cases, charge carrier holes become partially polarized due to the anisotropic modification of holes spectra caused by spin-orbit interactions, and this polarization exerts spin torque sufficient to rotate ferromagnetic domains. (C) 2012 Elsevier B.V. All rights reserved

    CCDC 1448927: Experimental Crystal Structure Determination

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    An entry from the Cambridge Structural Database, the worldā€™s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.An entry from the Cambridge Structural Database, the worldā€™s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures
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