Results 11 - 20 of 110225
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[en] The structure and properties of quasicrystals are discussed. The short-and long-range atomic orders and the effect of these factors on the physical characteristics are considered. It is noted that investigations of the physical properties of quasicrystals at temperatures above room temperature should be performed. Promising applications are briefly outlined
[en] Many years and great effort have been spent constructing the microscopic model for the room temperature multiferroic BiFeO3. However, earlier models implicitly assumed that the cycloidal wavevector was confined to one of the three-fold symmetric axes in the hexagonal plane normal to the electric polarization. Because recent measurements indicate that can be rotated by a magnetic field, it is essential to properly treat the anisotropy that confines at low fields. We propose that the anisotropy energy confines the wavevectors to the three-fold axis and within the hexagonal plane with .
[en] This paper presents the design, fabrication and calibration of a novel two-dimension microforce sensor with nano-Newton resolution. The sensor, mainly composed of a clamped–clamped beam (horizontal detecting beam), an overhanging beam (vertical detecting beam) and a half-folded beam, is highly sensitive to microforces in the horizontal (parallel to the probe of the designed sensor) and vertical (perpendicular to the wafer surface) directions. The four vertical sidewall surface piezoresistors (horizontal piezoresistors) and two surface piezoresistors (vertical piezoresistors) were fabricated to achieve the requirements of two-dimension microforce measurements. Combining the sensor structure with Wheatstone bridge configurations, the microforce decoupling among the x , y , and z direction can be realized. Accordingly, the sensor is capable of detecting microforces in the horizontal and vertical directions independently. The calibration results verified that the sensor sensitivities at room temperature are 210.58 V N−1and 159.2 V N−1 in the horizontal and vertical directions, respectively. Additionally, the sensor’s corresponding force resolutions are estimated at 2 nN and 3 nN in theory, respectively. The sensor can be used to measure the contact force between manipulating tools and micro-objects, in fields such as microassembly and biological assays. (paper)
[en] Thermally evaporated (Fe 3 nm/Dy 2 nm) multilayers have been magnetically and chemically investigated. Three-dimensional atom probe (3DAP) images related to multilayers revealed diffuse interfaces as well as the presence of Fe in Dy layers. Magnetic hysteresis loops measured on planar layers deposited on flat Si substrates show that the perpendicular magnetic anisotropy is much higher for the multilayers deposited at 600 K as compared to 320 K. 3DAP elemental maps show concurrently that the layered structure is degraded at 600 K. 3DAP analysis concerning an Fe/Dy multilayer deposited at 320 K on flat-topped Si posts is presented, and shows asymmetric interfaces
[en] We have carried out a high magnetic field study on single crystalline stoichiometric , a material discussed in terms quantum criticality in itinerant ferromagnets, by means of high field resistivity experiments. Our experiments have been performed at the Laboratoire National des Champs Magnétiques Intenses in Toulouse, France. The resistivity of single crystalline , has been investigated in external fields up to 15.5 T aligned along the c-axis in the temperature range of 1.4–55 K. The main focus of our study lies on the method to extract TN from the magnetoresistivity measurements, because TN could not be easily observed in temperature dependent resistivity for stoichiometric .
[en] Thermoacoustics in cryogenics continues to be a very interesting phenomenon which is still poorly understood but often experienced unexpectedly in experiments where it causes unacceptable heat leaks. The authors report on the appearance and onset of this unwanted occurrence at temperatures below 35 K. A number of physical experiments are presented, where the authors had the means to take quantitative measurements of the heat leak caused by these pressure oscillations in apparatus with bent tubes ranging from 4.55 and 4.7 mm inner diameter, with heat stationing links. The parameters which indicate the likelihood of inadvertently developing these thermoacoustic oscillations are presented and means developed to avoiding them in that instance are given. Furthermore, we had the rare opportunity to record and analyze 4 K TAOs experienced on a test setup and present the simple method that was used to eliminate them. (paper)
[en] Complete text of publication follows. In the previous research of cryogenic complex (dusty) plasma we observed experimentally the possibility of the formation of dust structures in cryogenic environment at 4.2-77 K. It was revealed from the experiments, among others, that the dust structures with high concentration of dust particles can be formed, in which interparticle distance is comparable with particle size - so-called superdense dusty plasma structures. Such structures had exotic properties such as globular (spherical) form, free boundaries, etc. In the present work new results on the experimental investigations of spheroidizing - phenomenon of the transition of dust structures to compact globular shape at cryogenic temperatures - were presented. The experiments were made by means of recently developed techniques and new cryogenic facilities (optical helium cryostat). Possible nature of such phenomenon is discussed.
[en] Results of studying stripe quantum cascade lasers emitting at room temperature in the spectral range of 4.8 µm are presented. Power characteristics and turn-on dynamics of the lasers upon pulse pumping are studied. The performed investigations demonstrate the presence of a significant heating of the active region during the pump pulse.
[en] In this article we present actual projects concerning high resolution measurements developed for future space missions based on ultracold atoms. This work involves the realization of a Bose Einstein Condensate in microgravitational environment and of an inertial atomic quantum sensor