National Institute of Technology, Nara College

Nara, Japan

National Institute of Technology, Nara College

Nara, Japan
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Matsuura Y.,National Institute of Technology, Nara College
Journal of Applied Physics | Year: 2013

I present a theoretical study on the spin-transport behavior of bimetallocenes of cobalt or nickel, wherein electronic communication between the two metal centers can be efficiently performed via a fulvalene ligand. The transmission of electrons in the bimetallocene connected to two gold electrodes was calculated using a first-principles density functional method. Spin transport was estimated from the difference between the transmissions of the spin-up and spin-down states. Results revealed that bicobaltocene has a perfect spin-filtering effect because the supply of excess electrons to the electronic state of ferrocene causes a split in the energy levels of the spin-up and spin-down states. As surmised, it was found that spin polarization was caused by strong interactions between the two metal centers via the fulvalene ligand. Furthermore, bicobaltocene exhibited a negative differential resistance at a relatively low bias voltage. © 2013 AIP Publishing LLC.


Wada T.,National Institute of Technology, Nara College
Materials Science Forum | Year: 2010

In cutting aluminum alloy 6061, continuous chips have a negative influence on the machining operation. Usually, Pb is added in order to break continuous chips. However, from the standpoint of environmental protection, it is necessary to improve chip breakability without adding Pb. One effective measure is improving chip breakability by adding Si in aluminum alloy 6061. However, the influence of Si content on tool wear has not been fully examined. In this study, in order to clarify the influence of a diamond-like carbon (DLC) coating layer on cutting performance, aluminum alloys having different Si contents were turned. The substrate of the tool material was high speed steel (1.4%C). The chip configuration, cutting force and tool wear were experimentally investigated. The following results were obtained: (1) The DLC coating layer was effective for decreasing the cutting force. (2) In cutting Al-2mass%Si alloy, the wear progress of the DLC-coated tool was slower than that of the un-coated tool. The length of a chip with the DLC-coated tool was shorter than that with the un-coated tool. © (2010) Trans Tech Publications.


Matsuura Y.,National Institute of Technology, Nara College
Chemical Physics Letters | Year: 2016

The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale. © 2015 Elsevier B.V. All rights reserved.


Matsuura Y.,National Institute of Technology, Nara College
Journal of Applied Physics | Year: 2014

The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended σ-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant β, which is defined as e-βL, of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge-Ge bond length is longer than the Si-Si bond length. © 2014 AIP Publishing LLC.


Matsuura Y.,National Institute of Technology, Nara College
Applied Physics Letters | Year: 2012

We focused on the spin transport properties of polymers containing ferrocene and the related transition-metal-benzene sandwich compound (metal = Cr and V) with a silicon bridge such as poly(ferrocenylsilane) and poly(metalarenylsilane). As a model system, a sulfur-substituted oligomer was put on gold electrodes via the sulfur-gold interaction. Spin transport between the two gold electrodes was calculated using a non-equilibrium Green's function formalism and density functional theory. We have found that the oligomer containing Cr or V atoms exhibited an almost perfect spin filter behavior in which all the 3d z 2 orbitals contributed to the electron transport. © 2012 American Institute of Physics.


Matsuura Y.,National Institute of Technology, Nara College
Journal of Chemical Physics | Year: 2013

I present a theoretical study of the electronic transport properties of nickelocenylferrocene sandwiched between gold electrodes. Compared with the biferrocene system, the nickelocenylferrocene system had high electrical conduction and rectification in the bias range -1 to 1 V. Furthermore, the spin-down states of the nickelocenylferrocene system exhibited perfect spin-filtering properties. From the electronic states of the nickelocenylferrocene, it was found that the rectification was caused by a difference in the bias-dependent behaviors between the Fe 3d and Ni 3d orbitals. © 2013 American Institute of Physics.


Uda R.M.,National Institute of Technology, Nara College | Ohshita M.,National Institute of Technology, Nara College
Biomacromolecules | Year: 2012

Photoinduced DNA compaction was performed using the interaction of DNA with a photoresponsive random copolymer of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). Although PVAMG does not have any affinity for DNA under dark conditions, it undergoes photoionization upon exposure to UV light, consequently resulting in a cationic binding site for DNA. Electrophoresis results demonstrated that irradiation of PVAMG retarded the DNA bands due to their complexation, whereas the bands remained unchanged under dark conditions. The binding of PVAMG to DNA occurs at a cationic site/DNA phosphate ratio of approximately 0.036. Single-molecule observations of DNA by fluorescence microscopy revealed that irradiation of PVAMG induced a coil-globule transition in the DNA molecule. Complete compaction of DNA has been accomplished at a cationic site/DNA phosphate ratio >8.0, indicating that PVAMG offers an effective system to photochemically trigger DNA compaction. © 2012 American Chemical Society.


Matsuura Y.,National Institute of Technology, Nara College
Solid State Communications | Year: 2011

Spin transport in bimetallic pentalene complexes (CpM(pentalene) M′Cp;M,M′=Fe,Co,Ni) between two gold electrodes was investigated, using a Green's function formalism under density functional theory. Variation of the metal atom species in the complexes gives a considerable change in their spin properties, with hetero-bimetallic complexes containing an odd number of electrons exhibiting spin filter behaviour. In contrast, alternation in the contact condition, whether Cp-anchoring or adducting by sulphurgold bonds, had almost no effect on spin filter behaviour, but did lead to variation in electrical conduction. We examined suitable bimetallic pentalene complexes in order to enhance their spin filter efficiency© 2011 Elsevier B.V. All rights reserved.


Matsuura Y.,National Institute of Technology, Nara College
Chemical Physics Letters | Year: 2016

Tunnel magnetoresistance (TMR) of diamondoids has been predicted by first principles density functional theory. Diamantane was used as a basic molecular proxy for diamondoids because hydrogen atoms in the apical position are easily substituted for a thiol group. The pristine diamantane exhibited a low TMR ratio of 7%, and boron-substitution considerably decreased the TMR ratio. Conversely, nitrogen-substitution enhanced the TMR ratio by up to 20%. Heteroatom-substitution changes the tunneling probabilities by varying the molecular bond lengths. Furthermore, when the spins of the electrodes are parallel, the heteroatoms resulted in transmittance probabilities at an energy range near the Fermi level. Consequently, heteroatom-substitution can control the TMR ratios of diamondoids very well. © 2016


Matsuura Y.,National Institute of Technology, Nara College
Chemical Physics Letters | Year: 2014

Spin conduction by a molecule-containing nitroxide radicals linked via a phenylene coupling unit was estimated by calculating the transmission of electrons in the molecule when sandwiched between two semi-infinite periodic gold crystals. Nitroxides linked via a m-phenylene coupling unit showed a large splitting in the energy of the transmission peaks of α- and β-spins, whereas this energy splitting was smaller for molecules with extended π-conjugation, such as nitroxides linked via a p-phenylene coupling unit. The energy splitting of transmission is influenced by spin polarization and constructive/destructive interference of radicals through the phenylene coupling unit. © 2014 Elsevier B.V. All rights reserved.

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