[en] Vortex lattice melting in the Hperpendicularc configuration of an YBa₂Cu₃O_6.94 single crystal has been investigated by means of the ac susceptibility χprime-iχdouble_prime and the magnetic torque τ. The melting transition of vortex lattice occurs in Hperpendicularc, too. Since the torque curve shows a sharp peak in the irreversible torque at θ_c ≅ 90degree due to intrinsic pinning at lower temperatures, the authors can determine the irreversibility line for the intrinsic pinning. The melting transition in the Hperpendicularc configuration appears at temperatures where the intrinsic-pinning peak is absent. They consider that the intrinsic pinning does not affect the nature of the vortex melting transition in the Hperpendicularc configuration

[en] In this report, large isometric oxide superconductor YBa₂Cu₃O_x single crystals and their flux pinning properties are reviewed. (J.P.N.). 84 refs

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[en] The interplane (cb) and intraplane (ab) anisotropy of untwinned YBa₂Cu₃O₇ single crystals has been investigated by means of the torque magnetometry. To extract the reversible and irreversible components, the torque was measured as a function of increasing angle as well as decreasing angle. The interplane irreversible torque τ_irr shows two-fold peaks at θ_c = 90 degrees and 270 degrees (of half width 11 degrees at 77 K) due to the well-known intrinsic interplane pinning. A novel intrinsic pinning has been discovered in the intraplane irreversible torque, i.e., τ_irr shows four-fold peaks of half width 20 degrees at 77 K when θ_a = 0 degrees, 90 degrees, 180 degrees and 270 degrees. The authors argue that the intrinsic intraplane pinning comes from the four-fold nature of the gap parameter

[en] A strontium or strontium oxide epitaxial layer was grown using a monoatomic buffer layer of hydrogen on silicon, in spite of a huge lattice mismatch. The onset of the initial growth stage of strontium crystals occur with only one atomic layer deposition. To investigate the growth mechanism in the highly mismatched system, combination analysis using neutron reflection, reflection high-energy electron diffraction, x-ray photoelectron spectra, and stress measurements is employed. The interface structure has opened up a new way to fabricate novel heterostructures, consisting of various kinds of one-, two- or three-dimensional materials for future silicon-based technology.

[en] We investigated the homogeneity of high-purity YBa₂Cu₃O_x (123) single crystals at different oxygen concentrations by means of the higher-harmonic susceptibility. The superconductivity of the onset temperature at 93.8 K was observed in the samples of the hypostoichiometric composition (x=6.87). Also, we succeeded in obtaining the 123 single crystals of the optimum stoichiometry (x=7.00) which showed a sharp single transition at 92.5 K corresponding to occurrence of the homogeneous superconductivity. (author)

[en] Graphene is a perfect impermeable membrane for gases but permeable to hydrogen ions. Hydrogen ion permeation shows the isotope effect, i.e., deuteron is slower than proton when permeating graphene. However, the permeation mechanism and the origin of the isotope effect are still unclear. Here, we propose a strategy to discuss the hydrogen ion permeation mechanism of graphene by developing an ion source with ultraslow, monochromatic, and mass-selected hydrogen ion beam. We employed a hemispherical monochromator and a Wien filter for the ion source to achieve the energy and mass resolutions of 0.39 eV and 1 atomic mass unit, respectively. The energetically sharp ion beam is expected to allow us to directly measure the permeability of graphene with high accuracy. (author)

[en] Morphological development of oxide islands on Si(001)-2x1 surfaces during the initial stage of dry oxidation has been studied using scanning tunneling microscopy. The oxidation was conducted at a substrate temperature of 560degC under an oxygen pressure of 6.7x10^-5 Pa. The initial oxide islands grow one-dimensionally until the number of oxygen atoms within an island reaches four, at which point the growth is converted into a two-dimensional growth mode. (author)

[en] We examine the effective regime for intrinsic pinning of an YBa₂Cu₃O_6.94 single crystal in the H-T plane. The irreversibility line for intrinsic pinning can be tracked by the hysteresis of the magnetic torque when the field is almost in parallel to the ab plane. The melting transition in the H perpendicular c configuration appears at higher temperatures where the intrinsic-pinning peak is absent. We argue that the intrinsic pinning may not affect the nature of the vortex melting transition in the H perpendicular c configuration. (author)

[en] The initial oxidation of a Si(110)-16x2 clean surface, both at room temperature (RT) and elevated temperatures (635, 660degC), was investigated by scanning tunneling microscopy (STM). The effects of annealing (300degC, 15min) on an RT-oxidized surface were also investigated. On the RT-oxidized surface, a BN site, detected as a bright (B) spot in the filled-state image but as a normal (N) 16x2 adatom in the empty-state image, was observed. After annealing, DD, BD, and BB sites were found to exist in addition to the BN site. Here, DD (BD, BB) is a site that appears dark (bright, bright) in its filled-state image and appears dark (dark, bright) in its empty-state image. The relative population is DD>BD approx. = BN>BB. For oxidation at 635degC, DD, BD, and BN sites were observed. For oxidation at 660degC, only the BD site was observed. On the basis of these results, an atomistic process during the initial oxidation of the Si(110)-16x2 surface is discussed. (author)