277 research outputs found
BaFe_{1.8}Co_{0.2}As_2 thin film hybrid Josephson junctions
Josephson junctions with iron pnictides open the way for fundamental
experiments on superconductivity in these materials and their application in
superconducting devices. Here, we present hybrid Josephson junctions with a
BaFe_{1.8}Co_{0.2}As_2 thin film electrode, an Au barrier and a PbIn counter
electrode. The junctions show RSJ-like current-voltage characteristics up to
the critical temperature of the counter electrode of about 7.2K. The
temperature dependence of the critical current, IC, does not show an
Ambegaokar-Baratoff behavior. Well-pronounced Shapiro steps are observed at
microwave frequencies of 10-18GHz. Assuming an excess current, I_ex, of 200
{\mu}A at 4.2K we get an effective I_C R_N product of 6 {\mu}V.Comment: submitted to Appl. Phys. Let
Influence of the spreading resistance on the conductance spectrum of planar hybrid thin film SNS' junctions based on iron pnictides
To investigate the superconducting properties of iron pnictides we prepared
planar hybrid SNS' junctions in thin film technology with a pnictide base
electrode, a gold barrier layer and a lead counter electrode. Our design allows
characterization of the electrodes and the junction independently in a 4-probe
method. We show how both electrodes influence the measured spectra due to their
spreading resistance. While the Pb electrode has a constant resistance above
its , the contribution of the pnictide electrode is clearly
current-dependent and thus it needs a more advanced method to be corrected. We
present an empirical method, which is simple to apply and allows to deal with
the spreading resistance in our junctions to recalculate the actual conductance
and voltage of one junction at given temperature
Directional Roll-up of Nanomembranes Mediated by Wrinkling
We investigate the relaxation of rectangular wrinkled thin films
intrinsically containing an initial strain gradient. A preferential rolling
direction, depending on wrinkle geometry and strain gradient, is theoretically
predicted and experimentally verified. In contrast to typical rolled-up
nanomembranes, which bend perpendicular to the longer edge of rectangular
patterns, we find a regime where rolling parallel to the long edge of the
wrinkled film is favorable. A non-uniform radius of the rolled-up film is well
reproduced by elasticity theory and simulations of the film relaxation using a
finite element method.Comment: 4 pages, 4 figure
Response to Halatek and Frey: Effective two-dimensional model does account for geometry sensing by self-organized proteins patterns
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Magnetization dynamics of magnetic domain wall imprinted magnetic films
The influence of micromagnetic objects on the dynamic magnetic excitation in magnetic thin films is studied by imprinting periodic domain wall patterns through selective ion irradiation in exchange biased Ni81Fe 19/IrMn structures. For high domain wall densities an increased precessional frequency is achieved. The zero field resonance of the domain wall state hereby depends directly on the stripe period, showing a pronounced increase with decrease of domain wall spacing. With the abrupt annihilation of magnetic domain walls with an applied bias field a jump-like decrease in precessional frequency takes place. The experimental data and micromagnetic simulations prove that the characteristic collective dynamic mode for the domain wall configurations is attributed to strongly coupled tilted magnetization structure. This is evidenced by an overlapping Néel wall structure for the narrowly spaced imprinted antiparallel unidirectional anisotropy state. The controlled introduction of high density frozen-in micromagnetic objects is a novel way to control the dynamic magnetic properties of continuous magnetic thin films
АСР процесса горения в топке котла при реализации безмазутной растопки
In the last years laser-induced breakdown spectroscopy was introduced in various industrial applications. Automated inspection machines were developed capable to operate under harsh ambient conditions. As an example laser-induced breakdown spectroscopy-based inspection machines for the identification testing of fittings and tubes made of high-alloy steel will be presented. Within an inspection time of 2 seconds 100 spectra are gained yielding the signals of 12 elemental lines to identify more than 30 different high-alloy steel grades in order to prevent material mix-ups at the end of a production line prior to packaging and dispatch. More than 1.5 million products have been inspected within the last 5 years in routine operation. Requirements, concepts and design of such machines will be discussed considering the issues on analytical resolution and system monitoring. For the first time a data set of more than 10(exp 8) laser-induced breakdown spectroscopy measurements has become available, giving insight into the long-term behavior of the system performance. First evaluations of this data demonstrate the influence of laser power, sample position and temperature on the spectroscopic signals and the system state. Future demands on next-generation inspection machines based on laser-induced breakdown spectroscopy will be defined
Стабилизация движения робота по показаниям электронного компаса
Laser-induced breakdown spectroscopy has been applied to polymer samples in order to investigate the possibility of using this method for the identification of different materials. The plasma emission spectra of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polyethylene terephthylene (PET), and polypropylene (PP) have been studied. Spectral features have been measured - for example, the 725.7 nm chlorine line, the 486.13 mm H(?) line, and the 247.86 nm carbon line - whose evaluation with neural networks permits identification accuracies between 90 and 1 00 per cent, depending on polymer type
Smearing of phase transition due to a surface effect or a bulk inhomogeneity in ferroelectric nanostructures
The boundary conditions, customarily used in the Landau-type approach to
ferroelectric thin films and nanostructures, have to be modified to take into
account that a surface of a ferroelectric (FE) is a defect of the ``field''
type. The surface (interface) field is coupled to a normal component of
polarization and, as a result, the second order phase transitions are generally
suppressed and anomalies in response are washed out. In FE films with a
compositional (grading) or some other type of inhomogeneity, the transition
into a monodomain state is suppressed, but a transition with formation of a
domain structure may occur.Comment: 5 pages, 1 figure; the effective bias field is very large, the
estimate is adde
Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene
Two-dimensional electron systems subjected to a perpendicular magnetic field
absorb electromagnetic radiation via the cyclotron resonance (CR). Here we
report a qualitative breach of this well-known behaviour in graphene. Our study
of the terahertz photoresponse reveals a resonant burst at the main overtone of
the CR, drastically exceeding the signal detected at the position of the
ordinary CR. In accordance with the developed theory, the photoresponse
dependencies on the magnetic field, doping level, and sample geometry suggest
that the origin of this anomaly lies in the near-field magnetoabsorption
facilitated by the Bernstein modes, ultra-slow magnetoplasmonic excitations
reshaped by nonlocal electron dynamics. Close to the CR harmonics, these modes
are characterized by a flat dispersion and a diverging plasmonic density of
states that strongly amplifies the radiation absorption. Besides fundamental
interest, our experimental results and developed theory show that the radiation
absorption via nonlocal collective modes can facilitate a strong photoresponse,
a behaviour potentially useful for infrared and terahertz technology.Comment: 27 pages, 22 figure
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