Pleiades Publishing Ltd

The role of superexchange interaction in the formation of the ferromagnetic state of cobaltites in the La0.5Sr0.5Co1–xMexO3 (Me = Cr, Ga, Fe) systems and manganites La0.7Sr0.3Mn0.85M0.15O3 (M–Nb, Mg) with a perovskite structure has been studied. It was found that the ferromagnetic state in cobaltites can be implemented in some compositions without the mixed-valence effect of cobalt ions. The initial compound (x = 0) is ferromagnetic (ТС = 247 K) with the saturation magnetization close to 2μB (at T = 30 K) per formular unit. It has been shown that the chemical substitution of cobalt by chromium reduces the spontaneous magnetization to 0.3μB (at х = 0.2), while the substitution of cobalt by iron ions (х = 0.2) does not alter the magnetization. The obtained data are interpreted in the model of positive superexchange interactions between cobalt and iron ions and negative ones between cobalt and chrome. It has been shown that the La0.7Sr0.3Mn0.85Nb0.15O3 composition is ferromagnetic with ТС=145K, with a magnetic moment of 3.1 μB/Mn at 10 K, and no evidence of a cooperative orbital ordering in the manganite compounds has been revealed. Partial chemical substitution of Nb5+ ions by Mg2+ ones leads to the formation of Mn4+ ions, while it does not strengthen the ferromagnetic state. The strengthening of the structural distortions reduces the ferromagnetic component. It is assumed that the ferromagnetic state is caused by a significant hybridization of eg-orbitals of the manganese and oxygen ions, which strengthens the positive component of the superexchange interactions.

Một nghiên cứu thực nghiệm được báo cáo về ảnh hưởng của bức xạ UV hoặc IR không đồng nhất lên quá trình nano lithography bằng phương pháp oxy hóa anod địa phương do đầu kim gây ra, áp dụng cho các màng titan. Cả hai hình thức bức xạ đều được phát hiện là làm tăng độ đồng nhất của kích thước các đặc trưng và cải thiện độ phân giải của kỹ thuật lithography. Nghiên cứu cũng chỉ ra rằng bức xạ UV cho phép tạo ra một kênh dẫn với chiều rộng 11 nm.

The finite-element method (FEM) is used to calculate stresses in a square silicon pressure-sensing element. The stresses near the edges of the membrane are calculated and measured. Close agreement is achieved between the FEM predictions and experimental results. An empirical formula is constructed for the longitudinal component of stress at points outside the membrane. It is established that the normal component of stress should be considered when designing pressure sensors for use at applied pressures above 107 Pa.

Transients in shielded on-chip interconnections are studied theoretically for grounded and ungrounded shields. The model is based on analytical solutions to telegrapher's equations. The properties of interconnections and shields are identified that affect transients and propagation delays in signal lines. It is shown that cross coupling may exist between lines using a common shield. The magnitude of electromagnetic interference in shielded lines is estimated.

The data of X-ray diffraction characteristics of silver thiogallate (AgGaS2) single crystals grown by the Bridgman–Stockbarger (BS) method on the (001) face and chemical transport reactions (CTRs) on the (100) face are presented. The X-ray conductivity coefficient of AgGaS2 at 298 K varies within 0.97–10.63 and 0.22–3.20 min/R for samples grown by the BS and CTR methods, respectively, at an effective radiation hardness of $${{V}_{a}}$$ = 25 to 50 keV and dose rate $$E$$ = 0.75–78.05 R/min. The dependence of the stationary X-ray current on the X-ray dose in AgGaS2 single crystals has a power-law character.

The work presents short descriptions of ion beam methods and X-ray diagnostics in conditions of the total external reflection geometry with accent on the planar nanostructures peculiarities study. These objects specificity is described, and these are formulated tasks, which are more suitable for these method applications. Experimental results, which confirm the high efficiency of real objects investigation by these methods are discussed. Possible directions of ion beam analysis and X-ray methodical background on base of the planar X-ray waveguide-resonators application are pointed. The profit from its devises use is re-ndered.

Conditions under which electric discharges can arise in cavitation bubbles pulsating in a multibubble cavitation field are considered. Possible electric discharge types are discussed. It is shown that, in an electric breakdown in a cavitation bubble, the probability of the formation of a streamer (all the more, a leader) or corona discharge is negligibly small. It was found that, in a cavitation bubble, the development of an electron avalanche is most probable. The basic parameters of an elementary electron avalanche are estimated.

Solitary silicon nanorelief elements with different widths are studied with the use of a scanning electron microscope (SEM). From the video signal curves obtained in the secondary-slow-electron mode of SEM measurements, the dependences of the length of check segments G p (D ef) and L p (D ef), where D ef is the effective diameters of the SEM probe, are determined. The dependences are found to be linear for all four solitary protrusions, and as D ef is increased, the length G p increases and the length L p decreases. It is shown that the method of defocusing the SEM electron probe provides a means for determining the linear dimension of nanorelief elements with a near-rectangular profile by extrapolating the linear dependences G p (D ef) and L p (D ef) to D ef = 0. It is established that the invariant check segment representative of the linear dimension of a particular relief element is at the level (sl)aver = 0.80 ± 0.03 for silicon elements with different widths.

The paper is concerned with the modeling and simulation of film nucleation and growth in the case of diamond-like deposition of materials on a (100) surface. Semi-empirical methods of computational quantum chemistry are used to estimate the potential energies of carbon clusters, on whose basis possible mechanisms of monolayer growth are investigated and the influence of temperature and pressure on a film microstructure is assessed.