Electrical Spin Injection in a Ferromagnetic / Tunnel Barrier/ Semiconductor Heterostructure

We demonstrate experimentally the electrical ballistic electron spin injection from a ferromagnetic metal / tunnel barrier contact into a semiconductor III-V heterostructure. We introduce the Oblique Hanle Effect technique for reliable optical measurement of the degree of injected spin polarization. In a CoFe / Al2O3 / GaAs / (Al,Ga)As heterostructure we observed injected spin polarization in excess of 8 % at 80K.Comment: 5 pages, 4 figure

Propagation of Own Non- Axisymmetric Waves in Viscoelastic Three-Layered Cylindrical Shells

The relevance of the study of the dynamic movements of structures consisting of a thin-walled shell and a viscoelastic cylindrical cavity mounted on it is due to their widespread application in modern technology. The mechanical system under consideration consists of two concentric cylindrical shells with a viscoelastic filler (or cylinder) between the shells. The filler and shell can be firmly attached to the outer and inner shells along the entire cylindrical surface. The basic equations of small oscillations of the shell theory and the three-dimensional viscoelasticity theory are used to describe the oscillations of the “shell-filler-shell” system with the exact satisfaction of the contact boundary. The main purpose of the work is to develop a method and algorithm for calculating the problems of propagation and absorption of natural waves in a mechanical "shell-filler-shell" mechanical system. A calculation method based on Müller, Gauss and orthogonal running methods was developed. The Kirchhoff-Love and Tymoshenko hypotheses are used for the cylindrical shell. For dissipative homogeneous and non-homogeneous mechanical systems, the variation of the real and imaginary parts of the complex phase velocity from different system parameters was studied. For sufficiently long waves, Kirchhoff-Love and Tymoshenko hypothesized that the phase velocities of the first form were found to be well matched. It was also found that it is possible to use shell equations for shortwave, taking into account the compression of the filler. It was found that the increase in filler thickness was particularly significant for the relatively small thickness of the filler

Highly efficient room temperature spin injection in a metal-insulator-semiconductor light emitting diode

We demonstrate highly efficient spin injection at low and room temperature in an AlGaAs/GaAs semiconductor heterostructure from a CoFe/AlOx tunnel spin injector. We use a double-step oxide deposition for the fabrication of a pinhole-free AlOx tunnel barrier. The measurements of the circular polarization of the electroluminescence in the Oblique Hanle Effect geometry reveal injected spin polarizations of at least 24% at 80K and 12% at room temperature

Electron irradiation: from test to material tayloring

In this article, we report some examples of how high-energy electron irradiation can be used as a tool for shaping material properties turning the generation of point-defects into an advantage beyond the presumed degradation of the properties. Such an approach is radically different from what often occurs when irradiation is used as a test for radiation hard materials or devices degradation in harsh environments. We illustrate the potential of this emerging technique by results obtained on two families of materials, namely semiconductors and superconductors

Natural and forsed osculations of pipelines in contact with the Wincler medium

In this paper, the pipeline is modeled as a curved rod in contact with the Winkler medium. Linear oscillations of a curved viscoelastic rod lying on the Winkler base are considered. The general formulation of the problem of free oscillations of a spatially curved viscoelastic rod with variable parameters is reduced to a boundary value problem for a system of ordinary integro-differential equations of the 12th order with variable coefficients relative to eigenstates; it can be solved by the method of successive approximations. The relations allowing to present the solution of the boundary value problem for the rod in an analytical form are formulated. It is established that the dimensionless complex frequencies of natural oscillations of a spatially curved rod, while maintaining the elongation of the rod constant, do not depend on it. The Poisson's ratio has little effect on the dimensionless real and imaginary parts of the natural frequencies

Enhancement of Exciton Emission from Zno Nanocrystalline Films by Pulsed Laser Annealing

Pulsed ArF laser annealing in air and in hydrogen atmosphere improves the optical properties of ZnO nanostructured films. Independently on the ambient atmosphere, laser annealing produces two major effects on the photoluminescence (PL) spectra: first, the efficiency of the exciton PL increases due to decrease of the number of non-radiative recombination centers; second, the intensity of the defect-related orange band decreases because of the removing of excessive oxygen trapped into the films during deposition. However, annealing in the ambient air also increases the intensity of the green band related to oxygen vacancies. We show that the combination of laser annealing and passivation of oxygen vacancies by hydrogen results in films free of defect-related emission and keeps intact their nanostructural character

Nonequilibrium spin distribution in single-electron transistor

Single-electron transistor with ferromagnetic outer electrodes and nonmagnetic island is studied theoretically. Nonequilibrium electron spin distribution in the island is caused by tunneling current. The dependencies of the magnetoresistance ratio $\delta$ on the bias and gate voltages show the dips which are directly related to the induced separation of Fermi levels for electrons with different spins. Inside a dip $\delta$ can become negative.Comment: 11 pages, 2 eps figure

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets

Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure

Коррозия алюминиевого проводникового сплава E-AlMgSi (алдрей), легированного индием

The effect of impurities on the electrical resistance of aluminum is well understood. It is known that the conductivity of aluminum is 65.45 % of the conductivity of copper. The tensile strength of aluminum wires is 150—170 MPa, which, with equal conductivity, is about 65 % of the strength of a copper wire. Such strength of aluminum wires is sufficient to support its own weight and may be insufficient when overloaded with snow, ice or wind.One of the ways to increase the strength of aluminum wires is the use of aluminum alloys having increased strength with a sufficiently high conductivity. One representative of the group of such alloys is the alloy E-AlMgSi (Aldrey). The main hardener of this alloy is the Mg2Si phase, which gives aluminum high mechanical properties.The paper presents the results of a study of the kinetics of high-temperature oxidation and electrochemical corrosion of indium-doped aluminum conductor alloy E-AlMgSi (Aldrey). Using thermogravimetry, it was shown that indium additives and temperature increase the oxidizability of the E-AlMgSi alloy (Aldrey). In this case, the apparent activation energy of the oxidation of alloys decreases from 120.5 to 91.8 kJ/mol. The oxidation rate of alloys determined by the potentiostatic method in a NaCl electrolyte showed that the corrosion resistance of alloys with indium is 20—30 % higher than that of the original alloy. With increasing concentration of NaCl electrolyte in the electrochemical potentials of the alloys decrease, the corrosion rate increases regardless of their composition.Экономическая целесообразность применения алюминия в качестве проводникового материала объясняется благоприятным соотношением его стоимости и стоимости меди. Немаловажным является и то, что стоимость алюминия в течение многих лет практически не меняется.При использовании проводниковых алюминиевых сплавов для изготовления тонкой проволоки, обмоточного провода и т. д. могут возникнуть определенные сложности в связи с их недостаточной прочностью и малым числом перегибов до разрушения. В последние годы разработаны алюминиевые сплавы, которые даже в мягком состоянии обладают прочностными характеристиками, позволяющими использовать их в качестве проводникового материала.Одним из перспективных направлений использования алюминия является электротехническая промышленность. Проводниковые алюминиевые сплавы типа E-AlMgSi (алдрей) являются представителями данной группы сплавов. В работе представлены результаты исследования температурной зависимости теплоемкости, коэффициента теплоотдачи и термодинамических функций алюминиевого сплава E-AlMgSi (алдрей) с висмутом. Исследования проведены в режиме «охлаждения».Показано, что с ростом температуры теплоемкость и термодинамические функции сплава E-AlMgSi (алдрей) с висмутом увеличиваются, а значение энергия Гиббса уменьшается. Добавки висмута до 1 % (мас.) уменьшают теплоемкость, коэффициент теплоотдачи, энтальпию и энтропию исходного сплава и увеличивают энергию Гиббса