Controlling the Spin Polarization of the Electron Current in a Semimagnetic Resonant-Tunneling Diode

The spin filtering effect of the electron current in a double-barrier resonant-tunneling diode (RTD) consisting of ZnMnSe semimagnetic layers has been studied theoretically. The influence of the distribution of the magnesium ions on the coefficient of the spin polarization of the electron current has been investigated. The dependence of the spin filtering degree of the electron current on the external magnetic field and the bias voltage has been obtained. The effect of the total spin polarization of the electron current has been predicted. This effect is characterized by total suppression of the spin-up component of electron current, that takes place when the Fermi level coincides with the lowest Landau level for spin-up electrons in the RTD semimagnetic emitter

Strategie der schnittaufteilung. Еine wirksame methode zur leistungsanpassung und verbesserung des dynamischen schnittverhaltens beim planfräsen

Der Beitrag beinhaltet eine zusammenfassende Darstellung des Prinzips der Schnittaufteilung als Methode zur dynamischen Prozessstabilisierung beim Planfräsen. Es wird dargelegt, wie die Schnittaufteilung beim Fräsen durch die Kombination von WSP mit unterschiedlichen Formen prinzipiell realisiert werden kann. Neben der Erläuterung weiterer positiver Effekte wird auf die Nutzung der Schnittaufteilung zur Leistungsanpassung unter stabilen Bearbeitungsbedingungen eingegangen.В статті розглядається ефективний метод регулювання потужності фрезерування та покращення динамічних характеристик фрезерування. Запропоновано стратегію скорочення проходів

First Principles Analysis of Electron-Phonon Interaction in Graphene

The electron-phonon interaction in monolayer graphene is investigated by using density functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic phonon contribution that is much weaker than previously thought, revealing the role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the high values reported in suspended samples.Comment: 12 pages, 4 figure

Curvature-driven homogeneous Dzyaloshinskii-Moriya interaction and emergent weak ferromagnetism in anisotropic antiferromagnetic spin chains

Chiral antiferromagnets are currently considered for broad range of applications in spintronics, spin-orbitronics and magnonics. In contrast to the established approach relying on materials screening, the anisotropic and chiral responses of low-dimensional antifferromagnets can be tailored relying on the geometrical curvature. Here, we consider an achiral, anisotropic antiferromagnetic spin chain and demonstrate that these systems possess geometry-driven effects stemming not only from the exchange interaction but also from the anisotropy. Peculiarly, the anisotropy-driven effects are complementary to the curvature effects stemming from the exchange interaction and rather strong as they are linear in curvature. These effects are responsible for the tilt of the equilibrium direction of vector order parameters and the appearance of the homogeneous Dzyaloshinskii-Moriya interaction. The latter is a source of the geometry-driven weak ferromagnetism emerging in curvilinear antiferromagnetic spin chains. Our findings provide a deeper fundamental insight into the physics of curvilinear antiferromagnets beyond the $\sigma$-model and offer an additional degree of freedom in the design of spintronic and magnonic devices.Comment: 5 pages, 3 figures, 1 table, 33 references, supplementary informatio

Investigation of surface structure, electrokinetic and stability properties of highly dispersed Ho₂O₃-Yb₂O₃/SiO₂ nanocomposites

A series of highly dispersed Ho2O3–Yb2O3/SiO2 nanocomposites was synthesized using a liquid-phase method and examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), and photon correlation spectroscopy (PCS). X-ray fluorescence spectrometry (XRF) confirmed a similar amount of weight percentage of Ho, Yb and Si oxides in the prepared samples. Samples HoYbSi1 (Ho2O3:Yb2O3:SiO2 = 0.5:10:89.5, wt. %), HoYbSi2 (Ho2O3:Yb2O3:SiO2 = 1:10:89, wt. %) and HoYbSi3 (Ho2O3:Yb2O3:SiO2 = 2:10:88, wt. %) calcined at 550 °C are amorphous. TEM and SEM analysis confirm a sphere-like morphology with a quite homogeneous size and shape. As compared with the initial silica, the agglomerated particles of nanocomposites in the aqueous medium are in the range from 200 to 850 nm according to PCS data. The effect of anionic polyacrylic acid (PAA) adsorption on fumed silica (SiO2) and Ho2O3–Yb2O3/SiO2 nanocomposite surfaces on suspension stability was studied. The turbidymetry method was used to monitor the initial silica and triple nanooxides suspensions stability as a function of time

Study of influence of draughts technological parameters on mechanical properties and mikrostruture of forgings from steel 20

Представлено результати експериментального дослідження впливу технологічних параметрів осадки на механічні властивості та структуру поковок зі сталі 20. Аналіз отриманих даних свідчить, що збільшення величини геометричного фактору та укову призводить до підвищення межі плинності матеріалу та зниження тимчасового опору матеріалу. Геометричний фактор на відміну від укову має більший вплив на межу плинності матеріалу. Вплив укову і геометричного фактору на показники тимчасового опору матеріалу приблизно однаковий. У зв’язку з нерівномірністю розподілу накопиченої деформації у об’ємі продеформованого металу спостерігаються три характерні зони, розміри яких залежать від фактору форми та від величини діючих напружень. Деформація на поверхні контакту з деформуючим інструментом ускладнена дією сил тертя. Як наслідок, структура у цій зоні є менш однорідною. У двох інших зонах за оптимального режиму деформації спостерігаються приблизно однакові структура та механічні характеристики.Contains results of experimental research of influence of technological parameters of draught on the mechanical properties and structure of steel forgings 20. Purpose. Finding correlation between draught deformations mode and forgings properties and structure. Design/methodology/approach. As a result of the experiment obtained regression equation defining the degree and character of influence of factor of forging reduction and geometric factor on the mechanical properties of metal (yield strength and tensile strength). Also at work was performed general qualitative analysis of influence of parameters of sediments on the uniformity of microstructure, formed by the cross-sections of the experimental samples. Findings. geometric factor have more significant influence on the tensile strength than forging reduction level, and the equal influence on the yield strength. Increasing of value of the geometric factor and forgings reduction leads to increasing yield strength of material and reduce the tensile strength of the material. Geometrical factor as opposed to forging reduction has a greater influence on the yield strength of material. Influence of forging reduction and geometric factors on parameters of tensile strength of the material about the same. Originality/value. Variation of technological parameters of draught allows getting forgings with better properties and equable structure.Представлены результаты экспериментального исследования влияния технологических параметров осадки на механические свойства и структуру поковок из стали 20. Анализ полученных данных свидетельствует, что увеличение величины геометрического фактора и уков приводит к повышению предела текучести материала и снижение временного сопротивления материала. Геометрический фактор в отличие от уков имеет большее влияние на предел текучести материала. Влияние уков и геометрического фактора на показатели временного сопротивления материала примерно одинаково. В связи с неравномерностью распределения накопленной деформации в объеме продеформованного металла наблюдаются три характерные зоны, размеры которых зависят от фактора формы и от величины действующих напряжений. Деформация на поверхности контакта с деформирующим инструментом осложнена действием сил трения. Как следствие, структура в этой зоне является менее однородной. В двух других зонах при оптимальном режиме деформации наблюдаются примерно одинаковые структура и механические характеристики

Field-induced spin reorientation transitions in antiferromagnetic ring-shaped spin chains

Easy axis antiferromagnets are robust against external magnetic fields of moderate strength. Spin reorientations in strong fields can provide an insight into more subtle properties of antiferromagnetic materials, which are often hidden by their high ground state symmetry. Here, we investigate theoretically effects of curvature in ring-shaped antiferromagnetic achiral anisotropic spin chains in strong magnetic fields. We identify the geometry-governed helimagnetic phase transition above the spin-flop field between vortex and onion states. The curvature-induced Dzyaloshinskii-Moriya interaction results in the spin-flop transition being of first- or second-order depending on the ring curvature. Spatial inhomogeneity of the N\'eel vector in the spin-flop phase generates weak ferromagnetic response in the plane perpendicular to the applied magnetic field. Our work contributes to the understanding of the physics of curvilinear antiferromagnets in magnetic fields and guides prospective experimental studies of geometrical effects relying on spin-chain-based nanomagnets.Comment: 11 pages, 6 figure

Використання b-блокаторів у хворих з абдомінальним сепсисом

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