Pulsed Laser Deposition of Rocksalt Magnetic Binary Oxides

Here we systematically explore the use of pulsed laser deposition technique (PLD) to grow three basic oxides that have rocksalt structure but different chemical stability in the ambient atmosphere: NiO (stable), MnO (metastable) and EuO (unstable). By tuning laser fluence, an epitaxial single-phase nickel oxide thin-film growth can be achieved in a wide range of temperatures from 10 to 750 {\deg}C. At the lowest growth temperature, the out-of-plane strain raises to 1.5%, which is five times bigger than that in a NiO film grown at 750 {\deg}C. MnO thin films that had long-range ordered were successfully deposited on the MgO substrates after appropriate tuning of deposition parameters. The growth of MnO phase was strongly influenced by substrate temperature and laser fluence. EuO films with satisfactory quality were deposited by PLD after oxygen availability had been minimized. Synthesis of EuO thin films at rather low growth temperature prevented thermally-driven lattice relaxation and allowed growth of strained films. Overall, PLD was a quick and reliable method to grow binary oxides with rocksalt structure in high quality that can satisfy requirements for applications and for basic research

Superconductivity and Hydrogen Economy : A Roadmap to Synergy

Hydrogen as an energy carrier is a promising alternative to fossil fuels, and it becomes more and more popular in developed countries as a carbon-free fuel. The low boiling temperature of hydrogen (20 K or −253.15 °C) provides a unique opportunity to implement superconductors with a critical temperature above 20 K such as MgB2 or high-temperature superconductors. Superconductors increase efficiency and reduce the loss of energy, which could compensate for the high price of LH2 to some extent. Norway is one of the pioneer countries with adequate infrastructure for using liquid hydrogen in the industry, especially in marine technology where a superconducting propulsion system can make a remarkable impact on its economy. Using superconductors in the motor of a propulsion system can increase its efficiency from 95% to 98% when the motor operates at full power. The difference in efficiency is even greater when the motor does not work at full power. Here, we survey the applications of liquid hydrogen and superconductors and propose a realistic roadmap for their synergy, specifically for the Norwegian economy in the marine industry.publishedVersionPeer reviewe

Dendritic flux avalanches in a superconducting MgB2 tape

MgB2 tapes with high critical current have a significant technological potential, but can experience operational breakdown due to thermomagnetic instability. Using magneto-optical imaging the spatial structure of the thermomagnetic avalanches has been resolved, and the reproducibility and thresholds for their appearance have been determined. By combining magneto-optical imaging with magnetic moment measurements, it is found that avalanches appear in a range between 1.7 mT and 2.5 T. Avalanches appearing at low fields are small intrusions at the tape's edge and non-detectable in measurements of magnetic moment. Larger avalanches have dendritic structures

Dendritic flux avalanches in a superconducting MgB2 tape

MgB2 tapes with high critical current have a significant technological potential, but can experience operational breakdown due to thermomagnetic instability. Using magneto-optical imaging the spatial structure of the thermomagnetic avalanches has been resolved, and the reproducibility and thresholds for their appearance have been determined. By combining magneto-optical imaging with magnetic moment measurements, it is found that avalanches appear in a range between 1.7 mT and 2.5 T. Avalanches appearing at low fields are small intrusions at the tape's edge and non-detectable in measurements of magnetic moment. Larger avalanches have dendritic structures

Surface superconducting states in a polycrystalline MgB2_{2} sample

We report results of dc magnetic and ac linear low-frequency study of a polycrystalline MgB$_2$ sample. AC susceptibility measurements at low frequencies, performed under dc fields parallel to the sample surface, provide a clear evidence for surface superconducting states in MgB$_2$.Comment: 4 pages and 5 figure

Energy of dendritic avalanches in thin-film superconductors

A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great advantage, because of their unpredictable and non-reproducible nature. The relative losses in energy are much higher than the relative losses in moment

Excitation of Vortex-antivortex Pairs in Thin Superconducting Films

Direct imaging of the accumulation of magnetic flux and antiflux resulted from the excitation of vortex-antivortex pairs inside thin superconducting films is reported. Thin-film superconductors, like YBa2Cu3O7PrBa2Cu3O7 superlattices or NbN films grown by pulsed laser deposition were used in experiments. The superlattices provide enhanced pinning for vortices, facilitating imaging of accumulated flux, and feature nanoscale fractures ideal for excitation of vortex-antivortex pairs. The idea of experiment is to record images using specific magneto-optical mode that allows distinguishing between positive and negative magnetic field in the sample. Two types of fluxantiflux patterns are observed. In one type, flux and antiflux are entering on permanent defects, like nano-fractures formed in the process of film deposition. In another type, flux and antiflux patterns are formed by application of strong localized magnetic field and not are linked to permanent defects. In first type, the amount of flux and antiflux entering superconductor from defect is strongly affected by external magnetic field. In the second type, the permanent frozen pattern is hardly influenced by the field. An unusual and dramatic effect of the excitation of flux-antiflux dendritic avalanches is also reported

Nanomaterials for renewable energy economy

Renewal energy economy relies on a range of novel materials for efficient production, distribution and consumption of energy. Nano science is playing increasingly important role in design and production of these materials. Examples of nano applications in energy sector are given following original research on materials for energy economy with focus on transmission of energy. The research is focused on nano-modified superconductors and novel thermo-insulators. A forecast for future activity is given, which is expected to lead to better materials, for example, superconductors with higher critical temperature and/or higher critical current density. The processes and equipment to process nano-materials are also discussed. © 2017 Institute of Electrical and Electronics Engineers (IEEE

Magnetic Force Microscopy of Brain Microtubules

Being biological object, microtubules attract significant attention in physics, since it is believed that they are responsible for quantum processing of information in the brain. There were, however, no direct experiments checking such a statement. Recently, strong advancement in quantum computing took place utilizing properties of superconductors at low temperatures. Following this progress, it was proposed that brain microtubules are superconducting at room temperature allowing quantum processing of information. Moreover, the evidence of room-temperature superconductivity in brain slices containing microtubules was obtained by electrical transport measurements, and even specific scenario of quantum processing in the microtubules has been suggested. These results, however, are not yet accepted by the scientific community as there are no known attempts to reproduce them. Another step in proving superconductivity would be confirming ideal diamagnetism of microtubules, since ideal diamagnetism is more fundamental property of superconductivity than perfect conductivity, some features of which were seen indirectly, or the existence of energy gap, which was already confirmed by the transport measurements. Here brain microtubules are examined by the magnetic force microscopy. The evidence of strong diamagnetism and its sensitivity to the water content in the microtubules is obtained. This gives another strong argument in favor of the concept suggesting superconductivity-based quantum processing of information in living organisms