Compositional depth profiling of ultrathin oxynitride/Si interface using XPS

The atomic-scale compositional depth profiling of oxynitride/Si interface by applying the maximum entropy concept to the angle-resolved Si 2p photoelectorn spectra was performed after eliminating the effect of photoelectron diffraction on the Si 2p photoelectron spectra arising from Si substrate for oxynitride films containing the maximum nitrogen concentration of 3 and 6 at.% at the SiO₂/Si(1 0 0) interface. Although the distribution of intermediate oxidation states of Si depends on the amount of nitrogen atoms incorporated at the interface, total amount of intermediate oxidation states of Si does not depend on the nitrogen atoms incorporated at the interface.     

Anomalous upper critical field in ternary iron-silicide superconductor Lu2Fe3Si5

We report the upper critical field H_c2 in a ternary iron-silicide superconductor Lu₂Fe₃Si₅ with T_c  6 K obtained by the resistivity measurements. We find that H_c2 increases linearly with decreasing temperature down to T_c/3, and H_c2(T = 0) exceeds the orbital depairing field described by the Werthamer–Helfand–Hohenberg theory. We also find that the anisotropy of H_c2 is nearly independent of temperature and the angular dependence of H_c2 is well-described by the anisotropic Ginzburg–Landau model. These results strongly indicate the presence of two distinct superconducting gaps in Lu₂Fe₃Si₅ although the behavior is slightly different from that of the typical two-gap superconductor MgB₂.     

Low-temperature STM/STS studies on boron-doped (1 1 1) diamond films

We have performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on (1 1 1)-oriented epitaxial films of heavily boron-doped diamond (T_c∼5.4 K). We present that tunneling conductance spectra show temperature-dependent spatial variations. In the low-temperature region (T=0.47 K), the tunneling spectra do not show strong spatial dependence and a superconducting energy gap is observed independent of the surface morphology. In the high-temperature region (T=4.2 K), on the other hand, the tunneling conductance spectra show significant spatial dependence, indicating the inhomogeneous distribution of the superconducting property due to the distribution of boron atoms.     

An FEM identification procedure for a wing section within a class of finite Laurent series

This paper concerns a determination procedure for conformal mapping of a wing through a finite element computation of potential function associated with the flow of 2-dimensional perfect fluid around the given wing section. Through our numerical procedure a family of mappings is obtained in the forms of finite Laurent series for an initial wing section input. Each member of the family describes a wing section located in a neighboring domain of the input one. Some of them could be expected as modified versions of the original wing section input, although they could not recover completely it.Inputting the shape of wing section has ambiguity in practical cases of wing sections such as the NACA23012 wing section. We would like to postulate that our identification procedure should be employed in the determination process of numerical profiles of the wing section considered, since identified ones are significantly easier in numerical processing than the original input shape.     

Stackelberg Solutions to Multiobjective Two-Level Linear Programming Problems

In this paper, we consider a multiobjective two-level linear programming problem in which the decision maker at each level has multiple-objective functions conflicting with each other. The decision maker at the upper level must take account of multiple or infinite rational responses of the decision maker at the lower level in the problem. We examine three kinds of situations based on anticipation of the decision maker at the upper level: optimistic anticipation, pessimistic anticipation, and anticipation arising from the past behavior of the decision maker at the lower level. Mathematical programming problems for obtaining the Stackelberg solutions based on the three kinds of anticipation are formulated and algorithms for solving the problems are presented. Illustrative numerical examples are provided to understand the geometrical properties of the solutions and demonstrate the feasibility of the proposed methods.     

Weak magnetic order in the normal state of the high-Tc superconductor La2-xSrxCuO4

We report magnetization measurements in the normal state of the high transition temperature (high-Tc) superconductor La2-xSrxCuO4. A magnetic order in the form of hysteresis in the low-field magnetization is observed at temperatures well above Tc. The doping (x) dependence of the onset and strength of this order follows Tc(x) and falls within the pseudogap regime.     

Superconducting state of Sr2RuO4 under magnetic fields

The layered perovskite Sr₂RuO₄ exhibits unconventional superconductivity below 1.5 K. There are now several key experimental facts which indicate that its superconducting symmetry is spin-triplet, p-wave, but some important features of its gap structure still need to be determined. In order to address some of the outstanding issues, we have performed a study of its thermodynamic behavior in the field-temperature phase diagram. Specific heat measurements give evidence for multiple superconducting gaps. We will discuss implications of this in relation to the idea of “orbital-dependent superconductivity”. We will also present the results of a search for a second superconducting transition under the magnetic field applied precisely parallel to the quasi-two-dimensional plane.     

Anomalous shift of EPR field in the one-dimensional magnet TMMC

An anomalous angular variation of the paramagnetic resonance field is observed in the one-dimensional magnet TMMC at room temperature. The extremely large shift at 9.45 GHz cannot be explained by the static dipolar field and strongly suggests the dynamic effect.     

Half-field EPR line in the two-dimensional ferromagnet K2CuF4

Room temperature measurements of the half-field EPR line in the two- dimensional ferromagnet K₂CuF₄ are reported. Changes of the intensity and line-width vs the angle between the applied field and the c-axis indicate the necessity of an additional term in the perturbing Hamiltonian besides the dipolar interaction. Its appearance at half the main Zeeman field at each angle means that there is no observable dynamic effect on the shift of the resonance position in this salt.