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A superconducting KBi2 sample was successfully prepared using a liquid ammonia (NH3) technique. The temperature dependence of the magnetic susceptibility (M/H) showed a superconducting transition temperature (Tc) as high as 3.6 K. In addition, the shielding fraction at 2.0 K was evaluated to be 87%, i.e., a bulk superconductor was realized using the above method. The Tc value was the same as that reported for the KBi2 sample prepared using a high-temperature annealing method. An X-ray diffraction pattern measured based on the synchrotron X-ray radiation was analyzed using the Rietveld method, with a lattice constant, a, of 9.5010(1) A under the space group of Fd[3 with combining macron]m (face-centered cubic, no. 227). The lattice constant and space group found for the KBi2 sample using a liquid NH3 technique were the same as those reported for KBi2 through a high-temperature annealing method. Thus, the superconducting behavior and crystal structure of the KBi2 sample obtained in this study are almost the same as those for the KBi2 sample reported previously. Strictly speaking, the magnetic behavior of the superconductivity was different from that of a KBi2 sample reported previously, i.e., the KBi2 sample prepared using a liquid NH3 technique was a type-II like superconductor, contrary to that prepared using a high-temperature annealing method, the reason for which is fully discussed. These results indicate that the liquid NH3 technique is effective and simple for the preparation of a superconducting KBi2. In addition, the topological nature of the superconductivity for KBi2 was not confirmed.

We performed X-ray diffraction (XRD) and DC magnetic susceptibility measurements to elucidate the crystal structure and superconducting properties of KSr2Nb3O10. From the diffraction pattern indexing, it was found that KSr2Nb3O10 crystallizes with monoclinic symmetry, space group P21/m(11). We succeeded in preparing high temperature (HT) and low temperature (LT) phases of KSr2Nb3O10 powder samples synthesized by a conventional solid state reaction and an ion-exchange reaction, respectively. Superconductivity was observed at 4 K by Li intercalation and it was found that the superconducting volume fraction of the LT phase (~ 1.4%) is clearly larger than that of the HT phase (0.07%).

18 O-labeled water (Water-18 O) is a widely used starting material of 18 F-labeled diagnostic agents in positron emission tomography (PET). Conventionally, Water-18 O has been separated from other stable oxygen isotope species (16 O, 17 O) by water distillation or nitric oxide distillation. However, conventional methods are costly and may have safety issues. In 2004, we developed the first unit of our novel oxygen isotope separation process by cryogenic oxygen distillation to overcome these issues. To meet the needs of the market, we built a second unit in 2013 and a third in 2016. We are now operating three commercially viable separation units with a total capacity of 600 kg of Water-18 O per year.

Magnetic pulse welding (MPW) which is one of the impact welding methods is suitable for a wide variety of combinations of similar and dissimilar metals. The flyer plate is accelerated by electromagnetic force and collided to the parent plate. A characteristic wavy interface is formed. The impact velocity and impact angle of the flyer plate during impact are important parameters which affect the interface morphology. In the case of dissimilar metals (e.g. Al/Cu, Al/Fe), the intermediate layer (such as intermetallic compound (IMC)) is formed by wavy interface formation and local temperature increase. The intermediate layer often decreases the bonding strength. Wavy interface formation mechanism and temperature increase at the joint interface should be investigated in order to obtain the dissimilar metal joint with high bonding strength. In this study, the impact velocity and impact angle of the flyer plate were obtained by using ANSYS Emag-Mechanical. Based on the obtained impact velocity and impact angle of the flyer plate in the MPW, the wavy interface formation and temperature change were reproduced by using ANSYS Autodyn for solving non-liner dynamics problems. Al sheets and Cu sheets were joined by the MPW. The joint interface was observed by OM and SEM and compared to the simulation result.

The characteristics of field-effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this review together with the electronic and crystal structures of phenacenes. Phenacene molecules possess a low HOMO level and a wide band gap. The highest mobility observed in the phenacene thin-film FETs is 7.4 cm2 V–1 s–1 for [6]phenacene, and in single-crystal FETs the highest value is 6.3 cm2 V–1 s–1 for [7]phenacene. The phenacene thin-film FETs show O2-sensing properties unlike their single-crystal FETs. The bias-stress effect is fully investigated for phenacene single-crystal FETs. Furthermore, the low-voltage operation of phenacene single-crystal FETs with electric-double-layer (EDL) capacitors is reported. The temperature dependence of phenacene single-crystal FETs is reported to clarify the transport mechanism, which is suggestive of band-like transport.

O2 gas sensing behaviors are studied in picene thin film field-effect transistors (FETs) with hydrophobic polymer (Cytop™ or polystyrene) coated SiO2 gate dielectrics. Picene thin film FETs show a rapid reduction of hysteresis in transfer curves recorded in forward and reverse measurement modes, compared to a picene FET with hexamethydisilazane-coated SiO2. The picene FETs show very sensitive O2 gas sensing effects down to ∼10 ppm. A quantitative analysis is presented of the gate voltage (VG) dependent mobility induced by O2 exposure, i.e., the suppression of drain current at high VG.

The phase diagram of the mixed donor quasi one-dimensional (Q1D) metallic system (TMTSF1−xTMTTFx)2PF6 has been studied. The study on the mixed donor systems helps us to establish not yet clarified phase boundaries in the Q1D system. We showed dependencies of properties on the donor mixing percentage for crystal parameters, resistivity, ESR (intensity and line width). ESR results show clear changes in the susceptibility and line width around 40 K. This result may indicate the existence of new boundary determined by the microscopic method on the Q1D phase.

We performed the low-temperature and radio-frequency (rf) ESR of spherically molded single crystals of β-p-NPNN in order to re-investigate the ferromagnetic resonance (FMR). The symmetric FMR signals were clearly observed below 0.8 K for the first time. The resonance field for H//c is markedly shifted about 80 G higher than the EPR resonance field while the anisotropy of the resonance field is very weak when the magnetic field is applied within the ab-plane. These results clearly indicate the spin-hard axis is parallel to the c-axis. We estimate the magnetic anisotropy HK = 61 G using the FMR relation with uniaxial anisotropy.

The low-temperature structure analysis and low-temperature ESR were performed in the γ -phase of p -NPNN, which is considered to be as a quasi-one-dimensional ferromagnet above the antiferromagnetic ordering temperature (0.65 K without a static magnetic field). No structural phase transition was observed below 30 K, but we found the large thermal shrinkage between the intra-chain p -NPNN molecules along c -axis. This result suggests that the one-dimensionality of the ferromagnetic chain is effectively enhanced at lower temperature, since the geometry through NO-NO 2 contact gives rise to the strong ferromagnetic interaction. Below 0.6 K, we succeeded in observing the antiferromagnetic resonance (AFMR) using the low frequency (∼300 MHz) and low-temperature (0.5 K) ESR. The frequency-field relation is well reproduced by the two-sublattice model with orthorhombic anisotropy.

We study the anisotropy of ESR parameters using single crystal TDAE-C 60 , which has two polymorphisms: the one is ferromagnetic a-phase and the other is non-ferromagnetic α′-phase. In both α′- and α-phase, the line-widths and g-factors show anisotropic angular dependences at room temperature, such as ΔH pp b > ΔH pp c ∼ ΔH pp a and g c > g b = g a . The anisotropic behaviour of g-factors in both phases suggest the uniaxial rotation of Jahn-Teller distorted C 60 molecules around the c-axis, which is the close-packing direction of C 60 molecules. In the α′-phase the temperature dependence of g-factors has a clear anomaly around 160 K. Below this temperature, the observed g-factors are in-between the monovalent C 60 and TDAE + , indicating the restoration of missing TDAE spins. In the α-phase, the g-factors continuously shift with decreasing temperature, become anisotropic below 230 K, and show no remarkable anomaly at the structural phase transition temperature. These results suggest that the difference exists in the mixing between the wave functions of C 60 and TDAE, which is possibly developed by the structural difference between α′- and α-phases. This difference separates the magnetic peculiarities of two polymorphisms in TDAE-C 60 .

We give an overview of our studies on the electron spin resonance (ESR) in the hexagonal triangular antiferromagnets of ABX 3 type using millimeter and submillimeter waves and static and pulsed high magnetic fields. Novel ESR modes, which cannot be understood by the conventional theory of the antiferromagnetic resonance, were observed. Examples of this include that there exists the gapless excitation even for the easy-axis anisotropy. The ESR modes can be classified by the signs of the exchange interaction J 0 along the c-axis and the anisotropy. The ESR modes were calculated within the framework of the mean-field approximation using three-sublattice and six-sublattice models for the ferromagnetic and antiferromagnetic J 0 interaction, respectively. The experimental results were well described by the present calculations.

Temperature dependence of electron spin resonance in Na2C60 was studied in a temperature range from 2 to 350 K. It was shown that Na2C60 was metallic above 50 K and had a metal-insulator transition at 50 K. The center frequency for the Hg(2) Raman mode in Na2C60 at 298 K was close to those in the metallic Rb3C60, K3C60, and Cs3C60, while the linewidth was close to that in the metallic but nonsuperconducting Cs3C60. The Hg(2) mode showed a large blueshift and narrowing at 50 K. The center frequency and the linewidth in the low-temperature region from 50 K were almost the same as those in the insulating C-60 and Rb6C60, which showed the metal-insulator transition at 50 K in Na2C60. The origin of this metal-insulator transition was discussed in terms of the electron-phonon interaction (Jahn-Teller effect) and the electron-electron interaction (Mott-Hubbard picture). [S0163-1829(99)04123-5].

The electron spin resonance (ESR) at low frequency (0.6–3 GHz) and at low temperature ( ∼ 0.5 K) was performed for the single molecular magnet V 15 . Non-linear field dependence of resonance at the lowest temperature implies the existence of the zero-field gap. The angle dependence of resonance field has strong anisotropy. We directly estimate the zero-field energy gap of 30 mK and analyze the energy levels using the model with Dzyaloshinskii–Moriya interaction.

The magnetization measurements under pressure were performed on the fullerene-based ferromagnet, α -TDAE- C 60 . We found that the saturation magnetization below the ferromagnetic ordering temperature T c is rapidly suppressed with increasing pressure and disappeared above P c 2 = 0.1 – 0.2 GPa . This pressure is remarkably lower than the critical pressure of polymerization P c = 0.7 GPa . On the contrary, T c is almost pressure independent below P c 2 , but, above P c 2 , could not be entirely determined because of the strong suppression of the magnetization. In the paramagnetic region, the susceptibility under pressure indicates the total number of spins remains unchanged around P c 2 as well as P c . We discuss these results compared with the high-pressure ESR.

Electron Spin Resonance (ESR) measurements have been performed on axial triangular antiferromagnets CsNiBr 3 and CsMnI 3 in their lowest three-dimensional (3 D) ordered phase. The frequency vs. magnetic field diagrams are obtained in the frequency range from 9 to 380 GHz and the magnetic field up to 160 kOe. Several significant disagreements between the experimental data and the theory based on the conventional model are found. It is shown that the disagreements can be removed by the diagonal interchain exchange coupling J 2 . The ESR theory is developed taking the J 2 coupling into account. Fitting the present theory to experimental data, the interaction parameters of CsNiBr 3 and CsMnI 3 are determined.

This article reviews new superconducting phases of carbon-based materials. During the past decade, new carbon-based superconductors have been extensively developed through the use of intercalation chemistry, electrostatic carrier doping, and surface-proving techniques. The superconducting transition temperature T c of these materials has been rapidly elevated, and the variety of superconductors has been increased. This review fully introduces graphite, graphene, and hydrocarbon superconductors and future perspectives of high-T c superconductors based on these materials, including present problems. Carbon-based superconductors show various types of interesting behavior, such as a positive pressure dependence of T c. At present, experimental information on superconductors is still insufficient, and theoretical treatment is also incomplete. In particular, experimental results are still lacking for graphene and hydrocarbon superconductors. Therefore, it is very important to review experimental results in detail and introduce theoretical approaches, for the sake of advances in condensed matter physics. Furthermore, the recent experimental results on hydrocarbon superconductors obtained by our group are also included in this article. Consequently, this review article may provide a hint to designing new carbon-based superconductors exhibiting higher T c and interesting physical features.

The electronic properties of Eu${}_{2.75}$C${}_{60}$ are studied using magnetic susceptibility and electron spin resonance (ESR) from 2 to 300 K. Both the magnetic susceptibility and the ESR parameters clearly show an anomaly around the valence transition temperature, ${T}_{\mathrm{V}}$ $=$ 70 K. The magnetic susceptibility shows weak temperature dependence above ${T}_{\mathrm{V}}$, while it changes drastically to Curie-Weiss behavior below ${T}_{\mathrm{V}}$. The low-temperature susceptibility can be reproduced by assuming the moment of free Eu${}^{2+}$ ions. This result reveals that Eu${}_{2.75}$C${}_{60}$ changes from the intermediate valence state to the divalent state below ${T}_{\mathrm{V}}$. Although ESR signals above ${T}_{\mathrm{V}}$ should be attributed to conduction electrons, the ESR intensity below ${T}_{\mathrm{V}}$ follows the Curie-Weiss law with a distinct increase in the $g$-factor. This should be associated with a strong localization of \ensuremath{\pi} electrons. We also found that, below \ensuremath{\sim}17 K, the isothermal magnetization exhibits a weak hysteresis and thermoremanent magnetization appears. These results suggest that valence-ordered Eu${}_{2.75}$C${}_{60}$ undergoes antiferromagnetic ordering with a weak ferromagnetic component at the N\'eel temperature, ${T}_{\mathrm{N}}$ $=$ 17 K.

We investigate the effects of a diagonal interchain interaction J 2 on the ESR modes in the A B X 3 -type antiferromagnets with easy-axis anisotropy.The static properties are described by replacing the conventional interchain interaction J 1 by J 1 -2 J 2 . However, because of the phase difference between the sublattice magnetizations, J 2 coupling produces marked effects on some ESR modes in cooperation with J 1 coupling. Large separation between the ω 1 -mode and EPR line for H ⊥ c and ω 2 - and ω 3 -modes for H // c ( H > H SF ) can be derived by maintaining consistency with the canting angle of spins from the c -axis and the spin wave dispersion at zero field. ESR measurements in CsMnI 3 are reported. The frequency-field diagram obtained is described well by the model involving J 2 coupling.

We have studied the ground state of a fullerene-based magnet, the alpha'-phase tetra-kis-(dimethylamino)ethylene-C-60 (alpha'-TDAE-C-60), by electron spin resonance and magnetic torque measurements. Below T-N = 7 K, nonparamagnetic field dependent resonances with a finite excitation gap ( 1.7 GHz) are observed along the a axis. Strong enhancement in their intensity as temperature is decreased is inconsistent with excitation from a singlet state, which had been proposed for the alpha'-phase ground state. Below T-N, nonquadratic field dependence of the magnetic torque signal is also observed in contrast to quadratic field dependence in the paramagnetic phase. The angle-dependent torque signals below T-N indicate the existence of an anisotropy of the bulk magnetization. From both experiments, we propose an antiferro-magnetic ground state driven by the cooperative orientational ordering of C-60 in the alpha'-TDAE-C-60.

High-pressure electron spin resonance (ESR) measurements were performed on tetrakis(dimethylamino) ethylene (TDAE)-C-60 single crystals and stability of the polymeric phase was established in the P-T parameter space. At 7 kbar the system undergoes a ferromagnetic to paramagnetic phase transition due to the pressure-induced polymerization. The polymeric phase remains stable after the pressure release. The depolymerization of the pressure-induced phase was observed at a temperature of 520 K, revealing an unexpectedly high thermal stability of the polymer. Below room temperature, the polymeric phase behaves as a simple Curie-type insulator with one unpaired electron spin per chemical formula. The TDAE(+) donor-related unpaired electron spins, formerly ESR silent, become active above a temperature of 320 K, which demonstrates that the magnetic properties are profoundly defined by miniscule reorientation of TDAE molecules.

In this paper, we propose a cell synthesis method for a Salicide process. Our method utilizes the local interconnect between adjacent transistors, which is available in some Salicide processes, and optimizes the transistor placement of a cell considering both area and the number of local interconnects. In this way we reduce the number of metal wires and contacts. The circuit model is not restricted to conventional series-parallel CMOS logic, and our method enables us to synthesize CMOS pass-transistor circuits. Experimental results show that our method uses the local interconnect effectively, and optimizes both cell area and metal wire length.

A layout approach for monolithic microwave integrated circuits (MMICs) is described, in which layout elements are transistors, inductors, capacitors, resistors, coplanar waveguides, etc., implemented in a GaAs fabrication process. The layout issue typical of such MMIC's consists essentially in how to realize a single-layered placement of different shapes of layout elements under a variety of spacing and orienting constraints as well as shape variations. In this paper, the interconnection requirements among the elements are represented by a graph, to which a planarization algorithm is applied. On the basis of the planarization result, the physical placement is first constructed with the use of a merging scheme and then refined iteratively by means of a new rectangle-packing algorithm. Experimental results are also shown to demonstrate the practicability of the described layout approach.

The magnetic ground state of the fcc phase of the Mott insulator Cs3C60 was studied using a low-temperature electron spin resonance technique, and antiferromagnetic resonance (AFMR) below 1.57 K was directly observed at ambient pressure. The AFMR modes for the fcc phase of Cs3C60 were investigated using a conventional two-sublattice model with uniaxial anisotropy, and the spin-flop field was determined to be 4.7 kOe at 1.57 K. The static magnetic exchange interactions and anisotropy field for fcc-Cs3C60 were also estimated.

Field-effect transistor (FET) devices using thin crystals of FeSe1−xTex (x = 0.9 and 1.0) have been fabricated with an electric-double-layer (EDL) capacitor. Despite the presence of substantial quantities of electron and hole carriers in the bulk due to the semimetallic electronic structure of FeSe1−xTex, we have observed p-channel depletion-type FET characteristics, in contrast to the n-channel normally on FET characteristics of a Bi2Se3 EDL FET. In FeSe1−xTex, the mobile carriers, holes, are depleted in the channel region by accumulating electrons, resulting in a decrease in conductivity. This result is consistent with the experimentally observed positive Hall coefficient at room temperature.

A layout approach is attempted dedicatedly for MMICs (monolithic microwave integrated circuits), on which predominant layout elements are transistors, resistors, capacitors, inductors, coplanar waveguides, T junctions, etc., formed by the GaAs fabrication process. The layout issue typical of such MMICs consists essentially in how to realize a single layer placement of different shapes of layout elements under a variety of spacing, orientating, and shaping constraints. Each layout element is modeled to simplify placement tasks subject to different placement constraints, and then a set of the interconnection requirements among elements is represented by a graph, to which a planarization algorithm is effectively applied. As a result of this planarization, a placement procedure is constructed mainly by repeated application of a merging scheme. A number of experimental results are also shown to demonstrate the practicability of the described layout approach.

Oxygen-17 is a stable oxygen isotope useful for various diagnostics in both engineering and medical applications. Enrichment of 17O, however, has been very costly due to the lack of appropriate methods that enable efficient production of 17O on an industrial level. In this paper, we report the first 17O-selective photodissociation of ozone at a relatively high pressure, which has been achieved by irradiating a gas mixture of 10 vol% O3-90 vol% CF4 with narrowband laser. The experiment was conducted on a pilot-plant scale. A total laser power of 1.6 W was generated by external-cavity diode lasers with all the laser wavelengths fixed at the peak of an absorption line of 16O16O17O around 1 μm. The beams were introduced into a 25 -m long photoreaction cell under the sealed-off condition with a total pressure of 20 kPa. Lower cell temperature reduced the background decomposition of ozone, and at the temperature of 158 K, an 17O enrichment factor of 2.2 was attained.

DMTCA-BF 4 (C = S, Se) have been considered as a quasi one-dimensional half- filled system. For both salts, the structural two-fold modulation along the stacking direction was observed from room temperature. We also found a rapid decrease in spin susceptibility of DMTSA-BF 4 below 100 K, but no anomaly at the metal-insulator transition temperature (150 K).

We have performed ESR measurements on the S = ½ double-spin-chain systems KCuCl 3 and TlCuCl 3 using single crystals. The ground states of these compounds are spin singlet and there are finite gaps in their excitation spectra. The temperature dependence of the paramagnetic resonance intensity is similar to that of susceptibility. The direct transition from the singlet ground state to the excited triplet state is observed for both compounds.

We have studied the ground state of an organic quasi-one-dimensional (Q1D) ferromagnet, the γ-phase para -nitrophenyl nitronyl nitroxide (γ- p -NPNN), by low-frequency ESR and magnetic torque measu...

Electron Spin-Echo (ESE) measurements on mixed-stack charge transfer compound tetrathiafulvalene (TTF)-chloranil (CA) are reported. Below Neutral-Ionic transition temperature, the ESE signals related to the spin solitons were observed. Comparing the phase memory time with the inverse of the EPR line-width, it was found that a crossover from fast motion of the spin solitons to slow motion took place around 70K. In addition, the spin-lattice relaxation measurements suggested the thermal fluctuation of the dimerized lattice above 60K.

The annealing effects on the magnetic and structural properties for organic ferromagnet C60 - TDAE are reported. The ESR line-width for unannealed single crystal shows a large hysteresis behavior around 130K. For the well-annealed crystal, on the other hand, the line-width continuously changed with temperature. In addition, the room temperature structural analysis of the single crystal indicated that all the crystal axes, especially c-axis, shrunk after annealing.

We investigate magnetic properties of an $S$=1/2 quasi-one dimensional organic antiferromagnet, D-F$_{5}$PNN using magnetization measurements taken at temperatures as low as 0.5 K. Three distinct phases were observed consisting of uniform, dimerized (D), and incommensurate (I) spin structures in the magnetic field versus temperature plane, where a significant hysteresis appears between D-I transitions in the field scan measurements. A combination of magnon ($S$=1) and soliton ($S$=1/2) excitations have successfully reproduced the observed magnetic susceptibility. In addition, such excitations provide a reasonable interpretation of the temperature dependent electron spin resonance (ESR) spectra. By comparison with the theoretical study, we conclude that D-F$_{5}$PNN is an ideal compound for investigating the spin-Peierls transition.