Effect of External Factors on the Ferromagnetic Resonance Line Width in Exchange-Biased Structures

Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The...     

<Emphasis Type="Italic">FCC/BCC</Emphasis> competition and enhancement of saturation magnetization in nanocrystalline Co-Ni-Fe films

The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B _s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.     

Ionization effects of the heavy components of cosmic radiation in protected chips

Radiation effects leading to degradation and failures in the operation of electronic equipment on board a space ship are of increasing concern in connection with the constantly decreasing sizes and increasing density of modern onboard microelectronics elements. The propagation of the energetic heavy ions of galactic cosmic rays (GCR) through a multi-layer structure (an integrated-circuit prototype) is discussed in the paper. The amount of electron-hole pairs induced by an ion in the sensitive area of a transistor has been estimated with consideration for energy losses in the chip body as well as in the protective oxide layers, contacts, and metallized layers. Calculation of the energy of various particles initiating the generation of a charge potentially capable to induce a single failure of onboard electronics has been carried out. The existence of a spatial region from which heavy fragments of a nuclear reaction, with a kinetic energy sufficient enough to induce a charge above the critical one, can penetrate into the gate region of a transistor has been demonstrated.     

Lifetime measurements on the compound nucleus 236U by means of the shadow effect

The lifetime of the ²³⁶U nucleus is measured in the range of excitation energies E_x = 6.7–11.5 MeV by a method based on the shadow (blocking) effect. The results obtained, as well as those of an earlier measurement of the lifetime for the ²³⁹U nucleus in the range E_x = 6.4–9.1 MeV, are compared with the results of calculations based on the level density ρ(E_x) in the Fermi-gas model and on the empirical level density ρ(E)_x) calculated as a result of an analysis of(n, γ) and (n, n') cross sections. An increase of excitation energy produces a substantial reduction in the rate of decrease of the lifetime at E_x ? 7.5 MeV for both compound nuclei as compared to the theoretical dependence τ(e_x).     

Planar detectors for multielement systems of millimeter-wave imaging

We discuss the concept of developing a millimeter-wave multielement matrix receiver on the basis of planar antennas with directly coupled low-barrier Schottky diodes. Three main problems are considered which involve choosing and developing a design of the planar antenna coupled with the low-barrier Schottky diode, optimizing the parameters of the low-barrier Schottky diodes for obtaining maximum sensitivity, and ensuring compact arrangement with weak mutual influence of the planar detectors in a two-dimensional array. We propose a design of the slot antenna with an active resistance of about 800 Ω at a resonant frequency of 94 GHz. The detection characteristics of diodes with the differential Schottky-barrier resistance in the range R_j = 0.4–1000 kΩ for a zero bias are studied experimentally. The mutual influence of the neighboring antennas is examined for developing the multielement radio-imaging system. The conditions of weak cross influence of the closely located planar detectors are determined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 12, pp. 1077–1087, December 2007.     

Ion-beam analysis of the structure and composition of nanocomposite nc-TiC/a-C:H coatings

The structure and composition of nanocomposite nc-TiC/a-C:H thin films prepared by closed-field unbalanced reactive magnetron sputtering in an argon-acetylene atmosphere have been investigated. The concentrations of carbon and heavier elements have been obtained by Rutherford backscattering and nuclear backscattering. The hydrogen concentration in the films has been determined by elastic recoil detection analysis. Based on the data obtained, a scheme has been proposed to evaluate the C:H matrix mass density and the sp ³ and sp ² fractions in the matrix.     

Exchange bias in the IrMn/Co structures with alternative sequences of antiferromagnetic and ferromagnetic layers

JETP Letters - The magnetic properties of Mo/IrMn/Co/Mo/SiO2/Si structures with alternative sequences of the antiferromagnetic and ferromagnetic layers have been studied by measuring the angular...     

Exchange bias in the IrMn/Co structures with alternative sequences of antiferromagnetic and ferromagnetic layers

The magnetic properties of Mo/IrMn/Co/Mo/SiO₂/Si structures with alternative sequences of the antiferromagnetic and ferromagnetic layers have been studied by measuring the angular dependence of the high-frequency radiation absorption in the ferromagnetic resonance region. The layers have been prepared by pulsed laser deposition in the absence of a magnetic field. It has been found that thermal annealing and cooling make it possible to create the exchange bias in the structure with the upper antiferromagnetic layer at a temperature much below the Néel temperature. At the same time, the identical heat treatment does not induce the exchange bias in the structure with the upper ferromagnetic layer. The possible mechanisms of the phenomena observed are discussed.     

Impact of high-energy cosmic-ray protons and ions on the elements of spacecraft on-board devices

The radiation environment in space is reviewed in short as an impact factor affecting onboard spacecraft electronics. The mass and energy distributions of the heavy component of space radiation and the contribution of galactic cosmic rays to the general flux are analyzed during a quiet period in solar activity. The nature of the limitations in the concept of linear energy transfer, including the effects of electronic semiconductor component crystallinity, is discussed. Protective measures against upsets in onboard electronics, caused by cosmic ray ions, are considered.