International audienceWe investigate proximity-induced superconductivity in micrometer-long bismuth nanowires connected to superconducting electrodes with a high critical field. At low temperature we measure a supercurrent that persists in magnetic fields as high as the critical field of the electrodes (above 11 T). The critical current is also strongly modulated by the magnetic field. In certain samples we find regular, rapid SQUID-like periodic oscillations occurring up to high fields. Other samples exhibit less periodic but full modulations of the critical current on Tesla field scales, with field-caused extinctions of the supercurrent. These findings indicate the existence of low dimensionality, phase coherent, interfering conducting regions through the samples, with a subtle interplay between orbital and spin contributions. We relate these surprising results to the electronic properties of the surface states of bismuth, strong Rashba spin-orbit coupling, large effective g factors, and their effect on the induced pair correlations. In particular, we emphasize the possible contribution of topological edge states of specific facets of the nanowires
A crystallographic approach to tailoring the morphology and ordering degree of the porous structure of alumina films obtained by anodization of single-crystalline aluminum is discussed. The examination of porous structure of anodic alumina films formed on low-index and vicinal planes of Al single crystals under self-ordering conditions by high-resolution small-angle Xray scattering revealed the existence of two pore growth directions on vicinal facets. The inclination of channels from the normal to the metal surface is explained by the competitive impact of electromigration driving force and the crystallographic anisotropy of the substrate. It was also shown that pores growing in different directions during anodization retain hexagonal domains with various in-plane orientations. These results for the first time demonstrate the strong correlations between the longitudinal alignment and in-plane packing options of pores in anodic alumina films.
The pseudoepitaxial growth of amorphous anodic alumina with ordered porous structure within single crystal grains of aluminum substrates is an amazing feature of the self-organization process, which occurs during anodization. Here, we used single crystal Al(100), Al(110), and Al(111) substrates to inspect the effect of aluminum crystallography on anodization rates and the morphology of the resulting alumina films grown under different anodization conditions. The difference in the kinetics of porous film growth on various substrates is described in terms of the activation barrier of aluminum atom release from the metal surface to the oxide layer. Scanning electron microscopy and small-angle X-ray scattering are applied for quantitative characterization of different kinds of ordering in anodic alumina films. The highest number of straight channels was found in porous anodic alumina grown on Al(100) substrates, whereas Al(111) was proved to induce the best orientational order in anodic alumina with the formation of the single-domain-like structures. Based on the obtained results, possible pathways for crystallographic control of the anodic alumina porous structure for different practical applications are discussed.
Single crystal nanoplatelets of M-type strontium hexaferrite, which were prepared by oxide glass crystallization, form colloidal solutions after consequent leaching and peptization of the nanocrystalline material. The colloids are stabilized by the particles charging to a zeta-potential of about 50 mV. Monolayers of oriented platelet strontium hexaferrite nanoparticles form readily on a glass surface while immersing the substrate in the colloidal solution due to Columb attraction of the positively charged nanoparticles to the negatively charged surface. The films show almost rectangular magnetization hysteresis loops typical for strongly textured hard-magnetic material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.