882 research outputs found
Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magnetic tunnel junctions
We report tunnel magnetoresistance (TMR) ratios as high as 472% at room
temperature and 804% at 5 K in pseudo-spin valve (SV) CoFeB/MgO/CoFeB magnetic
tunnel junctions (MTJs) annealed at 450oC, which is approaching the
theoretically predicted value. By contrast, the TMR ratios for exchange-biased
(EB) SV MTJs with a MnIr antiferromagnetic layer are found to drop when they
are annealed at 450oC. Energy dispersive X-ray analysis shows that annealing at
450oC induces interdiffusion of Mn and Ru atoms into the MgO barrier and
ferromagnetic layers in EB-SV MTJs. Mechanisms behind the different annealing
behavior are discussed.Comment: 13 pages, 5 figure
Atropisomeric Flavoenzyme Models with a Modified Pyrimidine Ring (BIOORGANIC CHEMISTRY-Bioorganic Reaction Theory)
Optically active 5-deazaflavin derivatives (3-aryl-10-(4-tert-butylphenyl)pyrimido[4,5-b]quinoline- 2,4(3H,10H)-dione) with an axial chirality at the pyrimidine ring have been synthesized, and the physical properties of these compounds have been investigated. In addition, (net) hydride-transfer reactions with NAD(P)H analogs have been carried out to elucidate the stereochemistry at the transition state of the reactions
Stereochemical Control in Microbial Reduction 11 : Enantioselective Reduction of β- and γ-Nitro Ketones with Bakers' Yeast (Commemoration Issue Dedicated to Professor Shinzaburo OKA On the Occasion of His Retirement)
A base pair at the bottom of the anticodon stem is reciprocally preferred for discrimination of cognate tRNAs by Escherichia coli lysyl- and glutaminyl-tRNA synthetases
Although the yeast amber suppressor tRNA(Tyr) is a good candidate for a carrier of unnatural amino acids into proteins, slight misacylation with lysine was found to occur in an Escherichia coli protein synthesis system. Although it was possible to restrain the mislysylation by genetically engineering the anticodon stem region of the amber suppressor tRNA(Tyr), the mutant tRNA showing the lowest acceptance of lysine was found to accept a trace level of glutamine instead. Moreover, the glutamine-acceptance of various tRNA(Tyr) transcripts substituted at the anticodon stem region varied in reverse proportion to the lysine-acceptance, similar to a ‘seesaw’. The introduction of a C31–G39 base pair at the site was most effective for decreasing the lysine-acceptance and increasing the glutamine-acceptance. When the same substitution was introduced into E.coli tRNA(Lys) transcripts, the lysine-accepting activity was decreased by 100-fold and faint acceptance of glutamine was observed. These results may support the idea that there are some structural element(s) in the anticodon stem of tRNA, which are not shared by aminoacyl-tRNA synthetases that have similar recognition sites in the anticodon, such as E.coli lysyl- and glutaminyl-tRNA synthetases
Consistent map building in petrochemical complexes for firefighter robots using SLAM based on GPS and LIDAR
The objective of this study was to achieve simultaneous localization and mapping (SLAM) of firefighter robots for petrochemical complexes. Consistency of the SLAM map is important because human operators compare the map with aerial images and identify target positions on the map. The global positioning system (GPS) enables increased consistency. Therefore, this paper describes two Rao-Blackwellized particle filters (RBPFs) based on GPS and light detection and ranging (LIDAR) as SLAM solutions. Fast-SLAM 1.0 and Fast-SLAM 2.0 were used in grid maps for RBPFs in this study. We herein propose the use of Fast-SLAM to combine GPS and LIDAR. The difference between the original Fast-SLAM and the proposed method is the use of the log-likelihood function of GPS; the proposed combination method is implemented using a probabilistic mathematics formulation. The proposed methods were evaluated using sensor data measured in a real petrochemical complex in Japan ranging in size from 550–380 m. RTK-GPS data was used for the GPS measurement and had an availability of 56%. Our results showed that Fast-SLAM 2.0 based on GPS and LIDAR in a dense grid map produced the best results. There was significant improvement in alignment to aerial data, and the mean square root error was 0.65 m. To evaluate the mapping consistency, accurate 3D point cloud data measured by Faro Focus 3D (± 3 mm) was used as the ground truth. Building sizes were compared; the minimum mean errors were 0.17 and 0.08 m for the oil refinery and management building area and the area of a sparse building layout with large oil tanks, respectively. Consequently, a consistent map, which was also consistent with an aerial map (from Google Maps), was built by Fast-SLAM 1.0 and 2.0 based on GPS and LIDAR. Our method reproduced map consistency results for ten runs with a variance of ± 0.3 m. Our method reproduced map consistency results with a global accuracy of 0.52 m in a low RTK-Fix-GPS environment, which was a factory with a building layout similar to petrochemical complexes with 20.9% of RTK-Fix-GPS data availability
Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperatur
We investigated the dependence of giant tunnel magnetoresistance (TMR) on the
thickness of an MgO barrier and on the annealing temperature of sputtered
CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO2/Si wafers. The
resistance-area product exponentially increases with MgO thickness, indicating
that the quality of MgO barriers is high in the investigated thickness range of
1.15-2.4 nm. High-resolution transmission electron microscope images show that
annealing at 375 C results in the formation of crystalline CoFeB/MgO/CoFeB
structures, even though CoFeB electrodes are amorphous in the as-sputtered
state. The TMR ratio increases with annealing temperature and is as high as
260% at room temperature and 403% at 5 K.Comment: 12 pages, 5 figure
Dependence of tunnel magnetoresistance on ferromagnetic electrode materials in MgO-barrier magnetic tunnel junctions
We investigated the relationship between the tunnel magnetoresistance (TMR)
ratio and the electrode structure in MgO-barrier magnetic tunnel junctions
(MTJs). The TMR ratio in a MTJ with Co40Fe40B20 reference and free layers
reached 355% at the post-deposition annealing temperature of Ta=400 degree C.
When Co50Fe50 or Co90Fe10 is used for the reference layer material, no high TMR
ratio was observed. The key to have high TMR ratio is to have highly oriented
(001) MgO barrier/CoFeB crystalline electrodes. The highest TMR ratio obtained
so far is 450% at Ta = 450 degree C in a pseudo spin-valve MTJ.Comment: 6 pages, 2 figures, 1 table. to be published in J. Magn. Magn. Mate
Incident-Angle-Dependent Extraordinary Transmission of the Terahertz Bull’s-Eye Structure
The bull’s-eye structure in the terahertz (THz) frequency region has ample applications owing to its ability to focus free-propagating waves into subwavelength apertures, resulting in enhanced transmission, that is, extraordinary transmission. However, its coupling properties have been primarily discussed in terms of the normal plane-wave incidence to the structure. In this study, we investigate the multiple resonances in extraordinary transmission with normal and oblique incident waves. The experiment using a widely tunable and high-power THz wave source revealed two types of resonances. The main resonance split depends on the incident angle, and the other corresponds to the side lobe of the main resonances. The results are explained by a simple analytical model using a finite number of scattering media. The analysis is supported by the full-wave simulation using the finite-element method, which agrees with the experimental results. The coupling mechanisms will be applicable to design devices, such as THz biosensing devices or THz antennas for rapid communication systems
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