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In this article, we provide an initial qualitative description of the basic magnetization reversal processes behind temperature and cooling field-dependent exchange bias effect at Co/CoO interface of Fe3O4/Alq3/Co/CoO/Au hybrid spin valve (SV) device structure. The exchange field at Co/CoO interface is observed to be inversely proportional to temperature, indicating enhanced magnetic field sensitivity of Co reverse domain nucleation at the high-temperature region. The exchange field, at constant temperature, is found to be insensitive to change in the cooling field, which may be due to efficient ferromagnetic coupling at the Co/CoO interface of the device. Sudden decrease of exchange field with training cycle number ($n$) has been observed at lower values of $n$ , which may be attributed to rearrangement of Co pinned layer spin configuration toward equilibrium. Interestingly, incorporation of antiferromagnetic CoO layer has not been observed to bring any change in magnetoresistance (MR) behavior of the exchange biased SV device, which shows a two-step switching pattern of MR at 100 K. [ABSTRACT FROM AUTHOR]

Low-temperature (< 10 eV) plasmas with densities varying over a very wide range from 10^13\ \m^-3 at the lower end to as high as 10^23\ \m^-3 have firmly established themselves as one of the most efficient and versatile tools to create and process materials at nanoscale. The dense plasma focus (DPF) device, which is a noncylindrical Z-pinch facility that compresses the plasma to very high energy densities, offers a complex mix of high energy ions of the filling gas species, immensely hot and dense decaying plasma, fast-moving ionization wave front, and a strong shockwave that provides a unique plasma and a physical/chemical environment that is completely unheard of in any other conventional plasma-based deposition or processing facility. This review aims to highlight the novel features offered by pulsed high-energy-density pinch plasmas from a DPF, having temperatures and densities a few orders of magnitudes higher than conventional low-temperature plasmas, in the processing and the synthesis of materials at nanoscale. The nanoscale fabrication using the DPF device is elaborated and discussed in two broad categories: 1) top–down nanoscale fabrication by processing of bulk or thin-film target materials that are placed downstream the anode axis by the energetic transient flux of energetic ions, the hot decaying plasma, the fast ionization wave front, and the shock front; and 2) bottom–up nanoscale fabrication by deposition of nanostructured thin films of metals and/or their nitrides, carbides, and oxides by ablating the metal fitted on to the anode top under suitable reactive or inert background plasma. [ABSTRACT FROM PUBLISHER]

A table top ~0.2-kJ miniature plasma focus (PF) device "FMPF-1" (2.4 µF, 27 ± 2 nH, T/4 ~400 ns, 9-14 kV) has been successfully used as a compact and portable, pulsed hard X-ray (HXR) source for fast (< 32-ns exposure time) radiography applications using Hydrogen (H2) as filling gas. The overall dimensions of the apparatus, which includes capacitor bank, sparkgap switch, and the focus chamber, are 0.2 m x 0.2 m x 0.5 m, and the system weighs about 25 kg. The time resolved information of HXR emission and their relative yield along the axial (0°) and radial (90°) directions are measured using a pair of cross-calibrated scintillator-photomultiplier detectors. The average pulse durations (full-width at half-maximum) of HXR pulse are measured to be 29±3 ns in axial direction and 18±2 ns in the radial direction. The average axial to radial HXR yield anisotropy is found to be 3.9 ± 0.9 at the optimum pressure of 3.5 mbar. The experimental estimation of the effective average energy of the HXR emission, with high-Z (Pb) insert in stainless steel anode is found to be in the range of 60-80 keV. The potential of the miniature PF as compact radiographic source is illustrated by radiographic imaging, with submillimeter range (< 0.3 mm) spatial resolution, of different objects placed outside the chamber. [ABSTRACT FROM AUTHOR]

Experiments show that the performance of the plasma focus (PF) depends on several macroscopic parameters like the energy of the capacitor bank, current, voltage, electrodes dimension, and curvature of current sheath in the axial phase. Recent work (IEEE Trans. Plasma Sci., vol. 24, no. 3, pp. 1101–1105, 1996) shows that overriding the dependence of performance on the individual parameters listed above is the dependence on a combined parameter called the drive or speed parameter S : (Ip/a)/ √ρ. This parameter S appears as most fundamental in the process of nondimensionalization of the magnetohydrodynamic equations coupling the highly supersonic motion of the plasma layer with the electromagnetic circuit equation. The drive parameter S is found to directly control the speed of the plasma layer in both axial and radial phases of the PEA literature survey (IEEE Trans. Plasma Sci., vol. 24, no. 3, pp. 1101–1105, 1996) first pointed out that neutron-optimized Mather-type PF devices with a range of energies from a few kilojoules to hundreds of kilojoules all operate with a remarkably constant drive parameter. This constancy of S has been extended more recently (Plasma Phys. Control. Fusion, vol. 47, pp. A361–A381, 2005) to PF devices over eight orders of magnitude of storage energies, from a fractional of a joule to megajoules. In this paper, experiments on 2–3,kJ dense PF with modified anodes have been conducted to show that this drive parameter remains fairly constant for the different ratios of the anode length to anode radius. It is also suggested that there may be significant differences in the values of drive parameters for Filippov-type focus devices, Mather-type focus devices, and also hybrid-type devices. [ABSTRACT FROM AUTHOR]

This paper investigates the emission characteristics of a high-performance low-energy (3-kJ) repetitive dense plasma focus device, NX2, operated at upto 1-Hz repetition rate to develop it as an intense source of soft X-rays (SXR) for microlithography and micromachining. Various SXR yield optimization studies with argon and neon as filling gases were performed under different operating conditions (charging voltage, filling pressure, anode length, and insulator sleeve length). The SXR yield was computed using signals obtained from a PIN diode SXR spectrometer with appropriate filters. When operated in neon, the avenge optimum SXR (λ ∼ 1 nm) yield in 4π steradians was found to be up to 140 J/shot, which corresponded to a wall plug efficiency of 5.6%. Operation in argon showed that optimized SXR (λ ∼. 0.4 nm) yield was up to 1.3 J/shot. While operating with neon under optimized conditions with a water-cooled anode in repetitive mode, the NX2 device was used as a SXR source to imprint a test lithograph on a highly sensitive chemically-amplified resist SU-8. Test structures showing the effect of a stepper with aspect ratio 3:1 on IO-pm-thick SU-8 resist film were obtained. [ABSTRACT FROM AUTHOR]