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The upper critical field μ0Hc2(Tc) of Tl0.58Rb0.42Fe1.72Se2 single crystals has been determined by means of measuring the electrical resistivity in both a pulsed magnetic field (∼58T) and a dc magnetic field (∼14T). It is found that μ0Hc2 linearly increases with decreasing temperature for H∥c, reaching μ0Hc2H∥c (0K)≃60T. On the other hand, a larger μ0Hc2(0K) with a strong convex curvature is observed for H⊥c [μ0Hc2H⊥c(18K)≃60T]. This compound shows a moderate anisotropy of the upper critical field around Tc, which decreases with decreasing temperature. Analysis of the upper critical field based on the Werthamer-Helfand-Hohenberg (WHH) method indicates that μ0Hc2(0K) is orbitally limited for H∥c, but the effect of spin paramagnetism may play an important role in the pair breaking for H⊥c. All these experimental observations remarkably resemble those of the iron pnictide superconductors, suggesting a universal scenario for the iron-based superconductors. Moreover, the superconducting transition is broadened significantly upon applying a magnetic field, indicating strong thermal fluctuation effects in the superconducting state of Tl0.58Rb0.42Fe1.72Se2. The derived thermal activation energy for vortex motion is compatible with those of the 1111-type iron pnictides. [ABSTRACT FROM AUTHOR]

GaP epilayers are grown on Si substrates after AsH3 preflow. Electron beam induced current observation and double-crystal x-ray diffraction show that the AsH3 preflow drastically improves crystalline quality of GaP epilayers. The full width at half-maximum of the (400) reflection obtained from 4.8 μm GaP is as small as 115 arcseconds. Secondary ion mass spectroscopy shows that As atoms accumulate at the GaP/Si interfaces, playing an important role in preventing Si outdiffusion into the GaP epilayers. [ABSTRACT FROM AUTHOR]

The dependence of the critical layer thickness hc on mole fraction x of Si1-xGex/Si heterostructures is determined by direct observations of misfit dislocations by using the electron beam induced current (EBIC) technique and transmission electron microscopy (TEM). The EBIC images of the Si1-xGex/Si interfaces show square-grid patterns running in the <110> directions. These patterns are identified by TEM observation to be misfit dislocations generated at the Si1-xGex/Si interface. The dependence of hc on x is compared with the results reported by R. People and J. C. Bean [Appl. Phys. Lett. 47, 322 (1985) and 49, 229 (1986)]. The comparison reveals that inconsistency exists between them, especially in the range of x<0.3. This inconsistency is considered to arise from the difference in the techniques adopted to determine the hc’s. [ABSTRACT FROM AUTHOR]

The magnetic-field-temperature phase diagram of solid oxygen is investigated by the adiabatic magnetocaloric effect (MCE) measurement with pulsed magnetic fields. Relatively large temperature decrease with hysteresis is observed at just below the β-γ and α-β phase-transition temperatures owing to the field-induced transitions. The magnetic field dependence of these phase boundaries are obtained as Tβγ(H)=43.8-1.55×10-3H² K and Tαβ(H)=23.9-0.73×10-3H² K. The magnetic Clausius-Clapeyron equation quantitatively explains the H dependence of Tβγ, but does not Tαβ. The MCE curve at Tβγ is of typical first order, while the curve at Tαβ seems to have both characteristics of first- and second-order transitions. We discuss the order of the α-β phase transition and propose possible reasons for the unusual behaviors. [ABSTRACT FROM AUTHOR]

Viscosity measurements in combination with pulsed magnetic fields are developed by use of a quartz-crystal microbalance (QCM). When the QCM is immersed in liquid, the resonant frequency, f0, and the quality factor, Q, of the QCM change depending on (ρη)0.5, where ρ is the mass density and η the viscosity. During the magnetic-field pulse, f0 and Q of the QCM are simultaneously measured by a ringdown technique. The typical resolution of (ρη)0.5 is 0.5%. As a benchmark, the viscosity of liquid oxygen is measured up to 55 T. [ABSTRACT FROM AUTHOR]

We developed a resistance measurement using radio frequency reflection to investigate the electrical transport characteristics under destructive pulsed magnetic fields above 100 T. A sample stage consisting of a homemade flexible printed circuit reduced the noise caused by the induced voltage from the pulsed magnetic fields, improving the accuracy of the measurements of the reflected waves. From the obtained reflectance data, the absolute value of the magnetoresistance was successfully determined by analyzing the phase with admittance charts. These developments enable more accurate and comprehensive measurements of electrical resistance in pulsed magnetic fields. [ABSTRACT FROM AUTHOR]

Magneto-caloric effects (MCEs) measurement system in adiabatic condition is proposed to investigate the thermodynamic properties in pulsed magnetic fields up to 55 T. With taking the advantage of the fast field-sweep rate in pulsed field, adiabatic measurements of MCEs were carried out at various temperatures. To obtain the prompt response of the thermometer in the pulsed field, a thin film thermometer is grown directly on the sample surfaces. The validity of the present setup was demonstrated in the wide temperature range through the measurements on Gd at about room temperature and on Gd3Ga5O12 at low temperatures. The both results show reasonable agreement with the data reported earlier. By comparing the MCE data with the specific heat data, we could estimate the entropy as functions of magnetic field and temperature. The results demonstrate the possibility that our approach can trace the change in transition temperature caused by the external field. [ABSTRACT FROM AUTHOR]

We present the architecture of the versatile nuclear magnetic resonance (NMR) spectrometer with software-defined radio technology and its application to the dynamically controlled pulsed magnetic fields. The pulse-field technology is the only solution to access magnetic fields greater than 50 T, but the NMR experiment in the pulsed magnetic field was difficult because of the continuously changing field strength. The dynamically controlled field pulse allows us to perform NMR experiment in a quasi-steady field condition by creating a constant magnetic field for a short time around the peak of the field pulse. We confirmed the reproducibility of the field pulses using the NMR spectroscopy as a high precision magnetometer. With the highly reproducible field strength, we succeeded in measuring the nuclear spin-lattice relaxation rate 1/T1, which had never been measured by the pulse-field NMR experiment without dynamic field control. We also implement the NMR spectrum measurement with both the frequency-sweep and field-sweep modes and discuss the appropriate choices of these modes depending on the magnetic properties of the sample to be measured. This development, with further improvement at a long-duration field pulse, will innovate the microscopic measurement in extremely high magnetic fields. [ABSTRACT FROM AUTHOR]

Ultrasound is a powerful means to study numerous phenomena of condensed-matter physics as acoustic waves couple strongly to structural, magnetic, orbital, and charge degrees of freedom. In this paper, we present such a technique combined with single-turn coils (STCs) that generate magnetic fields beyond 100 T with the typical pulse duration of 6 µs. As a benchmark of this technique, the ultrasound results for MnCr2S4, Cu6[Si6O18]·6H2O, and liquid oxygen are shown. The resolution for the relative sound-velocity change in the STC is estimated as Δv/v ∼ 10−3, which is sufficient to study various field-induced phase transitions and critical phenomena. [ABSTRACT FROM AUTHOR]

Single-turn coil (STC) technique is a convenient way to generate ultrahigh magnetic fields of more than 100 T. During the field generation, the STC explosively destructs outward due to the Maxwell stress and Joule heating. Unfortunately, the STC does not work at its full potential because it has already expanded when the maximum magnetic field is reached. Here, we propose an easy way to delay the expansion and increase the maximum field by using a mass-loaded STC. By loading clay on the STC, the field profile drastically changes, and the maximum field increases by 4%. This method offers access to higher magnetic fields for physical property measurements. [ABSTRACT FROM AUTHOR]

Bulk magnetoresistance quantum oscillations are observed in high quality single crystal samples of BiTel. This compound shows an extremely large internal spin-orbit coupling, associated with the polarity of the alternating Bi, Te, and I layers perpendicular to the c axis. The corresponding areas of the inner and outer Fermi surfaces around the A point show good agreement with theoretical calculations, demonstrating that the intrinsic bulk Rashba-type splitting is nearly 360 meV, comparable to the largest spin-orbit coupling generated in heterostructures and at surfaces. [ABSTRACT FROM AUTHOR]

The flow characteristics over a NACA4412 airfoil are studied in a low turbulence wind tunnel with moving ground simulation at a Reynolds number of 3.0 x 105 by varying the angle of attack from 0 to 10 deg and ground clearance of the trailing edge from 5% of chord to 100%. The pressure distribution on the airfoil surface was obtained, velocity survey over the surface was performed, wake region was explored, and lift and drag forces were measured. To ensure that the flow is 2-D, particle image velocimetry measurements were performed. A strong suction effect on the lower surface at an angle of attack of 0 deg at the smallest ground clearance caused laminar separation well ahead of the trailing edge. Interestingly, for this airfoil, a loss of upper surface suction was recorded as the airfoil approached the ground for all angles of attack. For angles up to 4 deg, the lift decreased with reducing ground clearance, whereas for higher angles, it increased due to a higher pressure on the lower surface. The drag was higher close to the ground for all angles investigated mainly due to the modification of the lower surface pressure distribution. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that the diamond-coated sliding surface has good quality with respect to sliding movement. We have ensured that the partly polished diamond-coated sliding surface shows much lower coefficients of the kinetic friction than the teflon-coated sliding surface in our experiments. Also, we confirmed that the gas-layer lubrication effect appears due to the gas in the concavo–convex sliding surface when its relative counter speed reaches in the order of 1 m/s. Then, in this study, the numerical investigation was performed to simulate the gas-layer lubrication effect on the sliding surface. The microscopic flow conducted in this study has very small length scale which is in the order of the mean-free path of the air at the atmosphere pressure. Consequently, the Navier–Stokes equations are not applicable to analyze the present microscopic flow because the continuum flow is assumed. In addition, we observed many unpolished concave parts on the diamond-coated surface after polishing, and the vertical flow will appear induced by such complicated geometric boundary. For this reason, any analytical method that assumes quasi-parallel flow cannot be applied to the present flow problem. Herein, we used direct simulation of Monte Carlo (DSMC) method to handle the nano/micro flow, which cannot be assumed to be continuum. We clarified the feature of gas-layer lubrication on the sliding surface, which would be dominated by the surface roughness, the relative counter speed of surfaces, and the surface roughness including its surface geometry in the nano/micro scales. [Copyright &y& Elsevier]

We investigated the effects of argon and hydrogen plasmas on the structure and electrical properties of the surface of silicon wafers. Surface roughness and defect density were measured by atomic force microscopy and photothermal deflection spectroscopy, respectively. The electronic properties of the silicon surfaces were evaluated by forming a Schottky contact on the plasma-treated surfaces. A significant surface roughness was observed on hydrogen-plasma-treated surfaces whereas the roughness on argon-plasma-treated samples was much smaller. Whereas the surface defect density was larger after argon plasma than after hydrogen-plasma treatment. Submitting an argon-plasma-treated surface to a subsequent hydrogen plasma reduced the density of defects created by the first treatment. The ideality factors of the Schottky barrier diodes were qualitatively consistent with the surface defect density. The hydrogen plasma reacts with the silicon surface and introduces surface roughness by breaking Si–Si bonds. The hydrogen atoms bond to the surface defects and consequently reduce the defect density. In contrast, the argon plasma sputters the silicon surface uniformly and hence creates defects. [Copyright &y& Elsevier]

We investigate low-temperature electronic properties of the nondimeric organic superconductor β′′-(ET)4[(H3O)Ga(C2O4)3]PhNO2. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below TCD∼8  K just above the superconducting critical temperature Tc∼6  K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that the superconducting gap function is fully gapped in the Fermi surface, but anisotropic with fourfold symmetry. We point out that the pairing mechanism of the superconductivity is possibly dominated by charge fluctuations. [ABSTRACT FROM AUTHOR]

We report a high-resolution terahertz spectroscopic study of quantum spin dynamics in the antiferromagnetic Heisenberg-Ising spin-chain compound BaCo2V2O8 as a function of temperature and longitudinal magnetic field. Confined spinon excitations are observed in an antiferromagnetic phase below TN ~ 5.5K. In a field-induced gapless phase above Bc = 3.8T, we identify many-body string excitations as well as low-energy fractional psinon or antipsinon excitations by comparing to Bethe ansatz calculations. In the vicinity of Bc, the high-energy string excitations are found to have a dominant contribution to the spin dynamics as compared with the fractional excitations. [ABSTRACT FROM AUTHOR]

We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H2O)4]SiF6⋅H2O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H2O)4]SiF6⋅H2O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field. [ABSTRACT FROM AUTHOR]

We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1/2 antiferromagnetic chain system BaCo2V2O8 as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of TN∼5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v(B) and a clear minimum of temperature T(B) at Bc,3D⊥=21.4 T, indicating the suppression of the antiferromagnetic order. At higher fields, the T(B) curve shows a broad minimum at Bc⊥=40  T, accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter ΓB∝(B-Bc⊥)-1. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model. [ABSTRACT FROM AUTHOR]