Spectroscopic ellipsometric evidence of the solid-state reactions in Ni/Si multilayered films,induced by ion-beam mixing and thermal annealing

Solid-state reactions, induced by ion-beam mixing (IBM) and thermal annealing, in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni2Si, NiSi and NiSi2, while keeping the nominal thickness of Ni sublayer constant (3.0 nm), were studied by using spectroscopic ellipsometry as well as X-ray diffraction (XRD). The mixing was performed with Ar+ ions of an energy of 80 keV and a dose of 1.5× 1016 Ar+/cm2. Unlike the results of our previous study on Fe/Si MLF [Y.V. Kudryavtsev et al., Phys. Rev. B 65, 104417 (2002)], it was shown that an amorphous phase of NiSi in the B20 phase was formed during deposition independent of the overall stoichiometry of MLF, i.e., the nominal thickness of Si sublayer. IBM leads to some structural changes in the Ni/Si MLF, which cannot be detected by XRD but are confidently recognized by optical tools. A thermal annealing at 673 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 causes formation of the -NiSi phase. The first trace of NiSi2 phase on the background of the -NiSi phase was detected by XRD after an annealing at 1073 K, while, according to the optical results, NiSi2 turned out to be the dominant phase for the annealed Ni/Si MLF with an overall stoichiometry of NiSi2.     

Influence of magnetic field sweep rate on the hysteresis loops of Ni0.8Fe0.2/Fe0.5Mn0.5 exchange bias bilayer

The influence of the magnetic field sweep rate on the hysteresis loops of exchange bias Ni0.8Fe0.2/Fe0.5Mn0.5 bilayers has been investigated with a vibrating sample magnetometer. It was found that the sweep rate of 13.6 kA/4πms is high enough to bring about obvious changes in the hysteresis loops of the exchange bias bilayer. High sweep rate in the magnetization reversal stage enlarges the coercivity of the sample, while high sweep rate in the saturation state reduces the coercivity. The above phenomena were attributed to magnetic viscosity in the ferromagnetic layer enhanced by the interface exchange interaction and domain magnetization reversals assisted by thermal fluctuation in the antiferromagnetic layer respectively.     

Oscillatory thickness dependence of magnetic moments and interface-induced changes of the exchange coupling in Co/Cu and CoNi/Cu multilayers

We perform first-principles calculations for the three multilayer systems (100)-Co₁/Cu_n, NiCo₂Ni/Cu_n and Co₄Cu_n, and find from a comparison of the results for system 2 and 3 that amplitude and phase of the exchange coupling are sensitive to the magnetic-slab/nonmagnetic-spacer interface. Moreover, we observe that for the system 1 the averaged magnetic moment of the magnetic slab oscillates with the spacer thickness similarly as the exchange coupling.     

Effects of rapid thermal annealing on the structural and electrical properties of Na-doped ZnMgO ?lms

Rapid thermal annealing (RTA) is a general approach to improve the crystallinity of thin solid films. In this study, we investigated the effects of RTA on the structural and electrical properties of Na-doped ZnMgO ?lms grown by pulsed laser deposition. X-ray diffraction (XRD) results showed that the crystallinity of the Na-doped ZnMgO ?lms was improved with RTA at 400-700 °C, and the grain size became larger as the annealing temperature increased. Moreover, room-temperature photoluminescence (PL) measurements demonstrated decent optical quality of the as-deposited and annealed Na-doped ZnMgO ?lms. Hall-effect measurements showed that the hole concentration increased from 4.9 × 10¹⁴ to 6.6 × 10¹⁵ cm⁻³ to 1.9 × 10¹⁷ to 8.3 × 10¹⁷ cm⁻³ while the resistivity and the Hall mobility decreased after the RTA treatments. The conduction type of the films converted from p to n when the annealing temperature is higher than 800 °C. Therefore a wide temperature window to obtain reasonable p-type Na-doped ZnMgO films by RTA is achieved. It is important because RTA is generally needed to obtain p-type Ohmic contact in the fabrication processes of light-emitting diodes (LEDs).     

Effects of annealing treatment and gamma irradiation on the absorption and fluorescence spectra of Cr:GSGG laser crystal

The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened markedly after the crystal was re-annealed in H₂ atmosphere, which is due to the Cr⁴⁺ ions being de-oxidized into Cr³⁺ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are ascribed to the Fe²⁺ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed.     

Role of annealing duration on the microstructure and electrochemical performance of β-V2O5 thin films

Vanadium pentoxide thin films have been prepared by sol–gel spin coating method. The eight-layered films coated on fluorine-doped tin oxide substrate and glass substrate were subjected to different durations of annealing under a constant annealing temperature of 300?°C from 30 to 120?min. The X-ray diffraction spectrum reveals crystallinity along (2?0?0) direction. The SEM images of these films show the variation in the surface morphology with increase in annealing duration. The supercapacitor behaviour has been studied using cyclic voltammetry technique and electrochemical impedance spectroscopy. The film annealed for 60?min exhibits a maximum specific capacitance of 346?F/g at a scan rate of 5?mV/s with a charge transfer resistance of 172 Ω.     

Magnetic properties of the υj15/2 intruder orbital in the superdeformed minimum of 197Pb

This work has established eight cross-talk transitions between the two signature partner superdeformed (SD) bands in ¹⁹⁷Pb with the EUROBALL IV spectrometer. Directional correlations from oriented states measurements confirm the ΔI = 1 character of these transitions. The flat behaviour of the dynamical moment of inertia and the agreement between the experimental and microscopic HF+BCS values of (g _K - g _R)K/Q ₀ suggest that the configuration of the SD bands is based upon the υ[752]5/2^- neutron intruder orbital. The derived effective spin gyromagnetic factor g _s ^eff is found to be not quenched, and is close to the theoretical g _s ^free value. Received: 14 June 2000 / Accepted: 14 September 2000     

A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys

The dynamic impact response of IN 718 and ATI 718Plus®, in both the solution heat treated and age-hardened conditions, were investigated at different deformation temperatures and strain rates using a direct impact Hopkinson pressure bar. Analyses of the results provide a vital but previously not reported information that the ATI 718Plus® offers a higher resistance to damage during high strain rate ballistic impact deformation compared to the most widely used Iron-nickel based superalloy, Inconel 718. ATI 718Plus® showed higher strain hardening and strain rate sensitivity, in both heat treatment conditions, than IN 718. The difference in the deformation behaviour of both alloys, in the annealed condition, is attributable to the compositional modification in ATI 718Plus® which has been reported to lower its stacking fault energy and increases the tendency for deformation twinning. However, in the age-hardened condition, the difference is believed to be related to the disparity in the operative strengthening mechanism, of the precipitates present in both alloys. Furthermore, a higher susceptibility to strain location and the formation of adiabatic shear band, in aged IN 718, is attributable to the stronger temperature-softening characteristics observed in the alloy and to the limited strain hardening tendency under dynamic impact loading.     

Magnetic behaviour investigation on symmetric spin valves of Co／Cu／NiFe and NiFe／Cu／Co

In this paper,we have obtained and investigated the magnetic behaviours of the ferromagnetic layer in the symmetric spin valves of Co/Cu/NiFe and NiFe/Cu/Co by measuring with a vibrating sample magnetometer and analysing in terms of the multi-domain Ising models.It has been found that some magnetic layer can have quite different magnetic behaviours in different structures of spin valves,depending on the properties of the under-layer.In our investigation,we have found that the magnetic behaviour of a Co layer depends mainly on the magnetization of the under-layer,whereas this is not the case for the NiFe layer.     

Refinement of the microstructure and enhancement of the magnetic properties in α-Fe/(Nd,Dy)2Fe14B nanocomposite using the two-step annealing technique

The Nd_8−xDy_xFe_87.5B_4.5 (x=0–1.0$x=0–1.0$) nanocomposites have been prepared by melt spinning and subsequent two-step heat treatment technique. The crystallization behaviors, microstructures and magnetic properties of the samples have been investigated. The experimental results show that the crystallization temperature of α-Fe soft phase has no obvious change through Dy addition while the crystallization temperature of 2:14:1 hard phase increases remarkably with increasing Dy content. By adopting a two-step heat treatment technique, a finer and more uniform microstructure can be developed. A dramatic enhancement of remanence J_r from 0.84 to 1.1 T, coercivity H_cj from 417 to 520 kA/m and energy product (BH)_m from 76.8 to 110 kJ/m³ have been obtained in Nd₇Dy₁Fe_87.5B_4.5 (30 vol%α-Fe ) nanocomposite.     

Influences of SiO_2 protective layers and annealing on the laser-induced damage threshold of Ta_2O_5 films

Ta_2O_5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO_2 protective layers and annealing on the laser-induced damage threshold(LIDT)of the films are investigated.The results show that SiO_2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly. Annealing is effective on decreasing the microdefect density and the absorption of the films.Both SiO_2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta_2O_5 films is achieved by the combination of SiO_2 protective layers and annealing.     

γ-Irradiation effects on the thermal decomposition behaviour and IR absorption spectra of piperacillin

The thermal decomposition behaviour of unirradiated and pre-γ-irradiated piperacillin (pipril) as a semi-synthetic penicillin antibiotic has been studied in the temperature range of (273–1072?K). The decomposition was found to proceed through three major steps both for unirradiated and γ-irradiated samples. Neither appearance nor disappearance of new bands in the IR spectrum of piperacillin was recorded as a result of γ-irradiation but only a decrease in the intensity of most bands was observed. A degradation mechanism was suggested to explain the bond rupture and the decrease in the intensities of IR bands of γ-irradiated piperacillin.     

Synthesis and Magnetic Properties of the Core–Shell Fe3O4/CoFe2O4 Nanoparticles

Physics of the Solid State - The Fe3O4/CoFe2O4 nanoparticles with a core–shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride...     

Plasma Dynamic Synthesis of Nanocrystalline WC1 – x and the Dependence of the Product Structure on the Ratio of Precursors

Technical Physics - The results of plasma dynamic synthesis of nanocrystalline cubic tungsten carbide using a system based on a coaxial magnetoplasma accelerator are presented. It is found that an...