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1.
Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions 总被引:3,自引:0,他引:3
The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs) is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM. 相似文献
2.
Toshiki Yamada Hidenori Shinohara Toshiya Kamikado Yoshishige Okuno Hitoshi Suzuki Shinro Mashiko Shiyoshi Yokoyama 《Thin solid films》2008,516(9):2522-2526
The spray-jet molecular beam apparatus enabled us to produce a molecular beam of non-volatile molecules under high vacuum from a sprayed mist of sample solutions. The apparatus has been used in spectroscopic studies and as a means of molecular beam deposition. We analyzed the molecular beam, consisting of non-volatile, solvent, and carrier-gas molecules, by using femtosecond- and nanosecond- laser mass spectroscopy. The information thus obtained provided insight into the molecular beam produced by the spray-jet technique. 相似文献
3.
Carrying out theoretical calculations using the density functional method for nonequilibrium electron transport, we investigated the electric conductibility of a porphyrin dimer coupled to gold electrodes by thiolate bonds. A porphyrin with four electron-donating amino groups in the dimer is connected to a porphyrin with four electron-withdrawing cyano groups by a dimethylene bridge. The calculations demonstrated that this dimer allows more flow of electrons from the first porphyrin (donor) to the second porphyrin (acceptor) than in the opposite direction. This means that the porphyrin dimer has favorable rectifier characteristics that are accounted for by the mechanism of not Aviram and Ratner [Chem. Phys. Lett. 29 (1974) 277] but of Stokbro, et al. [J. Am. Chem. Soc. 125 (2003) 3674]. 相似文献
4.
Yoshishige Kemmoku Keiko Ishikawa Shigeyasu Nakagawa Teru Kawamoto Tateki Sakakibara 《Electrical Engineering in Japan》2002,138(2):14-23
A photovoltaic/wind/diesel generating system with a battery (PWD system) is discussed from the viewpoint of total CO2 gas emissions during system lifetime. The total emissions are the sum of the emissions occurring at manufacturing and operating. First, the manufacturing CO2 emissions of the photovoltaic generator and the wind turbine generator are calculated by “the process analysis method.” This method considers the material used in each generator, its weight and its CO2 emission rate. On the other hand, the manufacturing CO2 emissions of the diesel generator and the battery are calculated using “the interindustry (input‐output) table.” Second, the PWD system is operated on a computer so that the fuel consumption of the diesel generator is a minimum assuming that hourly series data of electric load, insolation intensity, wind speed, and air temperature are known during the year. And CO2 emissions occurring at system operation are obtained from the annual fuel consumption of the diesel generator. The results show that CO2 total emissions of the PWD system are lower than those of the conventional diesel generator system. The CO2 total emissions reach a minimum when the photovoltaic/wind generating ratio is 50/50. The CO2 emissions of manufacturing decrease with increasing of the wind generating ratio from 100/0 to 0/100. The CO2 total emissions decrease as the natural energy ratio increases. It is, however, saturated to about 60% when the ratio is more than 60%. And the CO2 total emissions increase with increasing of the battery capacity. It is concluded that the PWD system plays an important role in decreasing considerably the CO2 total emissions while the total system cost is high under the present price circumstances. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 14–23, 2002 相似文献
5.
6.
Shigeki Sakaguchi Yozo Sawaki Yoshishige Abe Tadashi Kawasaki 《Journal of Materials Science》1982,17(10):2878-2886
Stable crack-propagation behaviour in silica glass as a raw material for optical fibres is studied under static tensile stress in various environments such as distilled water, NaCl aqueous solution, air and dry nitrogen gas, and the influence of these environments is discussed. The crack-growth rate in distilled water is obtained qualitatively as a function of the stress intensity factor and temperature, and the activation energy of the cracking process is determined as 97.6 kcal mol–1. The growth rate seems to be unaffected by Na+ and Cl– ions in an NaCl acqueous solution, but is influenced significantly by the humidity in the atmosphere. In a dry atmosphere, the growth rate in Region II cannot be expressed as a single function of the stress intensity factor. A plot of the log of time to failure against the initial stress intensity factor reveals a linear relationship in the environments tested. The critical fracture stress of an optical fibre is evaluated taking account of the crack size on the basis of fracture mechanics concept. 相似文献
7.
Shinichirou Orita Yoshishige Kemmoku Tateki Sakakibara Shigeyasu Nakagawa 《Electrical Engineering in Japan》1998,125(4):26-33
A single-stage neural network has been proposed to forecast next day insolation. In this paper, a multi-stage neural network is developed to reduce forecasting error further. A first-stage neural network forecasts average atmospheric pressure for the next day from atmospheric pressure data of the previous day. A second-stage neural network forecasts insolation level for the next day from the average atmospheric pressure and weather data of the previous day. A third-stage neural network forecasts next day insolation from the insolation level and weather data of the previous day. Meteorological data of Omaezaki, Shizuoka at April 1994 were chosen as input data. The insolation values forecasted by the multi-stage and the single-stage neural networks are compared with the measurement values. The results show that the forecasting error is reduced to 24% (by the multi-stage) from 33% (by the single-stage). © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 26–33, 1998 相似文献
8.
Naoyuki Harada Katsuyoshi Toyoda Tsuneaki Minato Tadashi Ichihara Takuya Kishida Tatsuo Koike Toru Izumi Yoshishige Murakami 《Electrical Engineering in Japan》1997,121(3):44-52
An Nb3Sn superconducting magnet to store 400 kJ was developed as a unit magnet for a 2.4-MJ SMES system used for stabilization studies of electrical power systems. The superconducting magnet consists of a cryostat and an Nb3Sn coil. The dimensions of the coil are: 340 mm inner diameter, 700 mm outer diameter and 177 mm axial length. The pool-cooled coil is a stack of 20 Nb3Sn double pancakes, and the cooling channels are aligned between pancake coils. To reduce Joule loss in electrical power converters, the maximum operating current of the coil is designed to be 350 A, which is one order of magnitude less than the operating currents of similar scale coils for pulse use. The conductor is an Nb3Sn monolithic conductor with cross section 1.50 × 2.38 mm. For good superconducting stability and high dielectric strength of the coil, the Nb3Sn double pancakes were wound by the react-and-wind technique. Operation of dc current to 105% (367.5 A) of the design operating current was achieved without quench. After the whole of the coil was exposed out of liquid helium, the coil did not quench under 120 A current operation for more than 2 hours. It was verified that the coil was stable for the SMES system. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 44–52, 1997 相似文献
9.
The influence of high concentrations of ferric ions on the biochemical activity of Acidithiobacillus ferrooxidans was studied using intact cells. The specific oxidation rate of ferrous ions decreased with increasing ferric ion concentration. Lineweaver-Burk plots revealed typical competitive inhibition kinetics, because the slopes varied with the ferric ion concentration. A linear relationship between the slope and the square of the ferric ion concentration revealed that the iron-oxidizing enzyme system of A. ferrooxidans was competitively inhibited by about two molecules of ferric ion. The kinetic equation based on this inhibition model agreed with the experimental observation at a high ferric ion concentration where the bacterium is usually exposed in bioleaching and biooxidation plants. 相似文献
10.
Takahiro Hayasaka Naoko Goto-Inoue Nobuhiro Zaima Yoshishige Kimura Mitsutoshi Setou 《Lipids》2009,44(9):837-848
Imaging mass spectrometry (IMS) has been developed as a method for determining and visualizing the distribution of proteins
and lipids across sections of dissected tissue. Although lipids play an important role in mammal development, their detailed
distributions have not been analyzed by conventional methods. In this study, we tried to determine and visualize lysophosphatidylcholine
(LysoPtdCho) and triacylglycerol (TAG) in a mouse embryo by matrix-assisted laser desorption/ionization (MALDI) hybrid quadrupole
time-of-flight (TOF) mass spectrometer. Many peaks were detected from a raster scan of the whole embryonic sections. The peaks
at m/z 496.33, 524.36, 879.72, 881.74, and 921.74 were identified by MS/MS analyses as [LysoPtdCho (16:0) + H]+, [LysoPtdCho (18:0) + H]+, [TAG (16:0/18:2/18:1) + Na]+, [TAG (16:0/18:1/18:1) + Na]+, and [TAG (16:0/20:3/18:1) + K]+, respectively. The ion images constructed from the peaks revealed that LysoPtdCho were distributed throughout the body and
TAGs were distributed around the brown adipose tissue and in the liver at embryo day 17.5. Thus, IMS system based on MALDI
hybrid quadrupole TOF MS revealed the distribution of LysoPtdCho and, more importantly, the organ-specific distribution of
TAGs in the embryonic stages of mammals for the first time. We can conclude that this technique enables us to analyze the
roles of various lipids during embryogenesis and gives insight for lipid research. 相似文献