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The rapid increase in the number of bacteria that are resistant to many commonly used antimicrobial agents and their global spread have become a major problem worldwide. In particular, for periodontal disease, which is a localized infection, there is a growing need for treatment methods that do not primarily involve antimicrobial agents, and antimicrobial photodynamic therapy (aPDT) is attracting attention. In this study, the bactericidal effects of a mid-infrared free electron laser (MIR-FEL) on E. coli were investigated as a basic study to examine the applicability of MIR-FELs, which can selectively excite molecular vibrations due to their wavelength tunability, to aPDT. The optimal irradiation wavelengths to be examined in this study were determined from the infrared spectrum of the bacteria, which was obtained using Fourier transform infrared spectroscopy. Five irradiation wavelengths (6.62, 6.88, 7.14, 8.09 and 9.26 µm) were selected from the FT-IR spectrum, and we found that the bactericidal effects at a wavelength of 6.62 µm were markedly stronger than those observed at the other wavelengths. At this wavelength corresponding to the Amide II band, the bacterial survival rate decreased significantly as the irradiation time increased. On the contrary, irradiation of a neodymium-doped yttrium aluminum garnet (Nd: YAG) laser at 1.06 µm exhibited no distinct bactericidal effect. No morphological changes were observed after MIR-FEL irradiation, suggesting that a bacterial organelle molecule may be the target of MIR-FEL irradiation, but the exact target was not identified. Furthermore, the temperature change induced in the culture medium by the laser irradiation was ± 1.5 °C at room temperature. These results suggest that the bactericidal effects of MIR-FEL are derived from photochemical reactions involving infrared photons, since E. coli is usually killed by heating it to 75 °C for 1 min or longer.

We have investigated the temperature- and field-variation of electronic state for the Dirac semimetal of ${\mathrm{EuMnBi}}_{2}$ by means of optical spectroscopy and theoretical calculation. The optical conductivity spectra show a clear Drude peak in the paramagnetic phase, which gradually diminishes in the Mn-$3d$ antiferromagnetic phase with decreasing temperature. Meanwhile, the absorption peaks due to the interband transition grow at low temperatures, resulting in a pseudogap feature with an energy scale of 0.07 eV. The analysis of Drude weight shows that the Drude response is nearly governed by the Dirac electrons at low temperatures. On the contrary, both the antiferromagnetic transition and spin reorientation of Eu-$4f$ moment do not significantly change the spectra except the moderate variation of Drude weight. As a comparison, we have also investigated the charge dynamics for ${\mathrm{EuZnBi}}_{2}$, which is an analog without the Mn-$3d$ antiferromagnetic ordering. In ${\mathrm{EuZnBi}}_{2}$, the optical conductivity spectra do not show the pseudogap structure, but show an intense Drude peak at all temperatures. Combined with the results of ab initio calculation, in ${\mathrm{EuMnBi}}_{2}$, it is likely that the reconstruction of electronic state driven by the Mn-$3d$ antiferromagnetic ordering causes the Dirac semimetallic state with tiny hole pockets, wherein electronic states other than the Dirac band are nearly gapped-out from the Fermi level.

${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ is one of the prototypical topological Dirac semimetals. Here, we manipulate the band inversion responsible for the emergence of Dirac nodes by alloying ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ with topologically trivial ${\mathrm{Zn}}_{3}{\mathrm{As}}_{2}$. The carrier density monotonically decreases and the resistivity is enhanced as $x$ is increased. For larger $x$, the thermoelectric figure of merit exhibits comparably large values exceeding 0.3 at room temperature, due to the combined effects of a strong enhancement of the thermopower, an only moderate increase in the resistivity, and a suppression of the thermal conductivity. Complementary quantum-oscillation data and optical-conductivity measurements allow us to infer that the Dirac nodes are gapped out, and a band structure with a partly flat dispersion likely emerges in the higher-$x$ region in ${\mathrm{Cd}}_{3\ensuremath{-}x}{\mathrm{Zn}}_{x}{\mathrm{As}}_{2}$.

We investigate the Seebeck and Nernst effects of pyrochlore iridium oxides (Nd1− xPr x)2Ir2O7 across the thermally induced and magnetic field-induced metal–insulator and topological transitions. Nd2Ir2O7 exhibits the salient temperature dependence of the Seebeck coefficient accompanied by the enhancement of the Nernst effect in the vicinity of the thermal magnetic transitions. Moreover, the Seebeck coefficient shows a remarkable magnetic field hysteresis with the differential magnitude reaching as large as 110 μV/K, as the conductive magnetic domain walls are generated/annihilated by the external field. For x = 0.5, the Nernst signal increases rapidly across the field-induced metal–insulator transitions, exceeding the values reported in existing ferromagnetic oxides. These findings indicate that the thermoelectric effects increase significantly near the topological electronic phase transitions in strongly correlated systems, providing a new guideline for thermoelectric material design.

Spin-charge conversion via spin-orbit interaction is one of the core concepts in the current spintronics research. The efficiency of the interconversion between charge and spin current is estimated based on Berry curvature of Bloch wave function in the linear-response regime. Beyond the linear regime, nonlinear spin-charge conversion in the higher-order electric field terms has recently been demonstrated in noncentrosymmetric materials with nontrivial spin texture in the momentum space. Here, we report the observation of the nonlinear charge-spin conversion in a nominally centrosymmetric oxide material ${\mathrm{SrIrO}}_{3}$ by breaking inversion symmetry at the interface. A large second-order magnetoelectric coefficient is observed at room temperature because of the antisymmetric spin-orbit interaction at the interface of Dirac semimetallic bands, which is subject to the symmetry constraint of the substrates. Our study suggests that nonlinear spin-charge conversion can be induced in many materials with strong spin-orbit interaction at the interface by breaking the local inversion symmetry to give rise to spin splitting in otherwise spin degenerate systems.

We have investigated the charge dynamics of the correlated Dirac semimetallic perovskite ${\mathrm{CaIrO}}_{3}$ by infrared spectroscopy. The optical conductivity spectra show the $\ensuremath{\omega}$-linear-type interband transition and a tiny Drude response at low temperatures, suggesting that the Dirac node is pinned near the Fermi energy due to the Mott criticality. Moreover, a large polaron absorption appears at around 0.04 eV, when thermally excited carriers diminish and the plasma frequency decreases below the optical phonon energy. The electron correlation and resultant reduced plasma frequency are likely to enhance the electron-phonon interaction via the insufficient electronic screening, realizing the Dirac polaron.

In this chapter, we review the recent research on the spin-state ordering in epitaxial thin films of perovskite LaCoO3 from the viewpoint of optical spectroscopy and X-ray scattering. A remarkable feature is that a variety of spin/orbital orderings, which have not been identified in bulk samples, can be induced by tuning the epitaxial strain in thin film samples. In the moderately tensile-strained films, a spin-state/orbital ordering accompanying the ordering of high-spin-state site and low-spin-state site occurs around 130 K, and subsequently, a ferromagnetic/ferrimagnetic ordering emerges around 90 K. In the weakly strained films, another spin-state/orbital ordered phase with longer modulation period emerges around 40 K, followed by a ferromagnetic ordering transition around 20 K. By analyzing the Co-3d orbital state by the resonant soft X-ray scattering technique, we identified that two kinds of high-spin state with different site symmetries emerges in this phase. Moreover, by means of grazing-incidence resonant soft X-ray scattering technique, it is demonstrated that the transition temperature of spin-state ordering is higher in the surface-layer of film than inside the film due to the strain relaxation. These results demonstrate that the strain engineering of epitaxial thin films offers a fertile playground to study the spin-state/orbital ordering in the correlated spin-crossover material.

We study possible Weyl semimetals of strongly correlated electrons by investigating magnetotransport properties in pyrochlore ${R}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ ($R$ denotes rare-earth ions), choosing three types of $R$ ions to design the exchange coupling scheme between $R\phantom{\rule{4pt}{0ex}}4f$ and Ir $5d$ moments: nonmagnetic Eu $(4{f}^{6})$, isotropic Gd $(4{f}^{7})$, and anisotropic Tb $(4{f}^{8})$. In the doping-induced semimetallic state, distinctive features of magnetoresistance and the Hall effect are observed in $R=\mathrm{Gd}$ and Tb compounds due to the effects of the exchange-enhanced isotropic and anisotropic Zeeman fields, respectively, exemplifying the double-Weyl semimetal and the two-in two-out line-node semimetal as predicted by theories. In particular, the Hall angle of an $R=\mathrm{Gd}$ compound is strongly enhanced to 1.5% just above the critical doping for the Mott transition. Furthermore, an unconventional Hall contribution is discerned for a lower doping regime of the $R=\mathrm{Gd}$ compound, which can be ascribed to the emergence of Weyl points with the field-distorted all-in all-out order state. These findings indicate that the hole-doping-induced Mott transition as well as the characteristic $f\text{\ensuremath{-}}d$ exchange interaction stabilizes versatile topological semimetal states in a wide range of material parameter space.

In the mixed-valence manganites, a near-infrared laser typically melts the orbital and spin order simultaneously, corresponding to the photoinduced d1d0→d0d1 excitations in the Mott-Hubbard bands of manganese. Here, we use ultrafast methods-both femtosecond resonant X-ray diffraction and optical reflectivity-to demonstrate that the orbital response in the layered manganite Nd1-xSr1+xMnO4(x=2/3) does not follow this scheme. At the photoexcitation saturation fluence, the orbital order is only diminished by a few percent in the transient state. Instead of the typical d1d0→d0d1 transition, a near-infrared pump in this compound promotes a fundamentally distinct mechanism of charge transfer, the d0→d1L, where L denotes a hole in the oxygen band. This finding may pave a different avenue for selectively manipulating specific types of order in complex materials of this class.

Epitaxial strain provides important pathways to control the magnetic and electronic states in transition-metal oxides. However, the large strain is usually accompanied by a strong reduction of the oxygen-vacancy formation energy, which hinders the direct manipulation of their intrinsic properties. Here, using a postdeposition ozone annealing method, we obtain a series of oxygen stoichiometric SrCoO3 thin films with the tensile strain up to 3.0%. We observe a robust ferromagnetic ground state in all strained thin films, while interestingly the tensile strain triggers a distinct metal-to-insulator transition along with the increase of the tensile strain. The persistent ferromagnetic state across the electrical transition therefore suggests that the magnetic state is directly correlated with the localized electrons, rather than the itinerant ones, which then calls for further investigation of the intrinsic mechanism of this magnetic compound beyond the double-exchange mechanism.

Significance Shift current is one of the bulk photovoltaic phenomena in the materials without inversion symmetry, originating from the geometric Berry phase of the constituting electron bands. This concept of photocurrent generation based on the real-space shift of the electron cloud on the short timescale of optical transition is distinct from that of conventional p–n junction photovoltaics, where the carriers are driven by the built-in Coulomb potential. We experimentally demonstrate for a ferroelectric polar semiconductor how the subpicosecond charge swing on the relevant chemical bond changes its dynamics while scanning the excitation photon energy across the bandgap. On the interband photoexcitation above the bandgap, a finite net charge flow is produced along the electrically polar direction., Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.

The impact of electron correlation on the Dirac semimetal state is investigated for perovskite ${\text{CaIrO}}_{3}$ in terms of the magnetotransport properties under varying pressures. The reduction of electron correlation with a pressure of 1 GPa enhances the Fermi velocity as much as 40%, but it reduces the mobility by an order of magnitude by detuning the Dirac node from the Fermi energy. Moreover, the giant magnetoresistance at the quantum limit due to the one-dimensional confinement of Dirac electrons is critically suppressed under pressure. These results indicate that the electron correlation is a crucial knob for controlling the transport of a correlated Dirac semimetal.

Topological quantum states of matter, characterized by geometrical features of electronic band structures, have been extensively studied. Among them, the topological electronic state with magnetic order remains elusive because of a scarce number of examples. Here we present experimental observations proving that the pyrochlore iridate, when electronically tuned, can be a topological Weyl semimetal as predicted by recent theories. We observe a sizable spontaneous Hall conductivity with minimal magnetization only within a few Kelvin below the all-in all-out magnetic ordering temperature. Our theoretical calculation, which is quantitatively consistent with the observation, suggests that the presence of linearly-dispersing crossing points (Weyl points), acting as a source/sink of a quantized magnetic flux, potentially gives rise to such an enormous effect. The manifestation of the salient Hall response provides one important example of topological states, which promotes a better understanding of Weyl semimetal and indicates the new research direction for the topological-materials design., Material with both topological state and magnetic order remains rare. Here, Ueda et al. observe a sizable spontaneous Hall conductivity with minimal magnetization at a few Kelvin below the all-in-all-out magnetic ordering temperature in the predicted magnetic Weyl semimetal R2Ir2O7.

The spin states of ${\mathrm{Co}}^{3+}$ ions in perovskite-type ${\mathrm{LaCoO}}_{3}$, governed by the complex interplay between the electron-lattice interactions and the strong electron correlations, still remain controversial due to the lack of experimental techniques which can directly detect them. In this Letter, we revealed the tensile-strain dependence of spin states, i.e., the ratio of the high- and low-spin states, in epitaxial thin films and a bulk crystal of ${\mathrm{LaCoO}}_{3}$ via resonant inelastic soft x-ray scattering. A tensile strain as small as 1.0% was found to realize different spin states from that in the bulk.

Visualizing conducting domain walls When a metal undergoes a phase transition and becomes insulating, it sometimes also becomes magnetically ordered. It is possible that some metallicity survives along the boundaries of magnetic domains, the so-called domain walls, but the question is difficult to address directly in experiments. Ma et al. did just that by mapping out the conductance of the material Nd 2 Ir 2 O 7 in its low-temperature magnetic insulating phase, using microwave impedance microscopy. The magnetic domain walls showed up clearly in the images as regions of high conductance. Science , this issue p. 538

We report the polarization rotation of terahertz light resonant with the magnetoelectric (ME) spin excitation in the multiferroic ${(\mathrm{Fe},\mathrm{Zn})}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$. This resonance reflects the frequency dispersion of the diagonal ME susceptibility (axion term), with which we quantitatively reproduce the thermal and magnetic-field evolution of the observed polarization rotation spectra. The application of the sum rule on the extrapolated dc value of the spectral weight of the ME oscillator provides insight into the dc linear ME effect. The present finding highlights a novel optical functionality of spin excitations in multiferroics that originates from diagonal ME coupling.

The development of antibiotics cannot keep up with the speed of resistance acquired by microorganisms. Recently, the development of antimicrobial photodynamic therapy (aPDT) has been a necessary antimicrobial strategy against antibiotic resistance. Among the wide variety of bacteria found in the oral flora, Porphyromonas gingivalis (P. gingivalis) is one of the etiological agents of periodontal disease. aPDT has been studied for periodontal disease, but has risks of cytotoxicity to normal stained tissue. In this study, we performed aPDT using protoporphyrin IX (PpIX), an intracellular pigment of P. gingivalis, without an external photosensitizer. We confirmed singlet oxygen generation by PpIX in a blue-light irradiation intensity-dependent manner. We discovered that blue-light irradiation on P. gingivalis is potentially bactericidal. The sterilization mechanism seems to be oxidative DNA damage in bacterial cells. Although it is said that no resistant bacteria will emerge using aPDT, the conventional method relies on an added photosensitizer dye. PpIX in P. gingivalis is used in energy production, so aPDT applied to PpIX of P. gingivalis should limit the appearance of resistant bacteria. This approach not only has potential as an effective treatment for new periodontal diseases, but also offers potential antibacterial treatment for multiple drug resistant bacteria.

We investigated magnetotransport properties and charge dynamics of strain-free perovskite ${\mathrm{SrIrO}}_{3}$. Both the longitudinal and transverse magnetoresistivity (MR) are significantly enhanced with decreasing temperature, in accord with the evolution of the Dirac semimetallic state. The electron correlation effect in the Dirac state shows up as a dramatic change in charge dynamics with temperature and as an enhanced paramagnetic susceptibility. We propose that the field-induced topological transition of the Dirac node coupled to the enhanced paramagnetism causes the unique MR of correlated Dirac electrons.

We report sub-picosecond photocarrier dynamics observed via emitted terahertz waves in a ferroelectric semiconductor Sn2P2S6. Excitation photon energy, intensity and polarization dependences of the photocarrier dynamics testify that the ultrafast photocurrent originates from the shift-current under interband excitation. The photocurrent excitation spectrum shows a quantitative agreement with that derived from first-principles calculations with the Berry connection integrated, showing the shift-current to be a sensitive feature in ferroelectrics. The terahertz emission spectroscopy is a powerful tool to identify the intricate carrier dynamics under pulsed photoexcitation.

Magnetic excitations are investigated for a hexagonal polar magnet $\mathrm{F}{\mathrm{e}}_{2}\mathrm{M}{\mathrm{o}}_{3}{\mathrm{O}}_{8}$ by terahertz spectroscopy. We observed magnon modes including an electric-field active magnon, electromagnon, in the collinear antiferromagnetic phase with spins parallel to the $c$ axis. We unravel the nature of these excitations by investigating the correlation between the evolution of the mode profile and the magnetic transition from antiferromagnetic to ferrimagnetic order induced by a magnetic field or Zn doping. We propose that the observed electromagnon mode involves the electric polarization oscillating within the $c$ plane induced by the collective precession of the spins through the same mechanism as producing the linear magnetoelectric effect.

High-resolution powder x-ray diffraction and single-crystal neutron diffraction were used to investigate the crystal structure and magnetic ordering of the compound $\mathrm{P}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{C}{\mathrm{a}}_{x}\mathrm{V}{\mathrm{O}}_{3}$ ($0\ensuremath{\le}x\ensuremath{\le}0.3$), which undergoes an insulator-to-metal transition for $x\ensuremath{\sim}0.23$. Since the ionic radii of $\mathrm{P}{\mathrm{r}}^{3+}$ and $\mathrm{C}{\mathrm{a}}^{2+}$ are almost identical and structural disorder is minimal, $\mathrm{P}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{C}{\mathrm{a}}_{x}\mathrm{V}{\mathrm{O}}_{3}$ is a good model system for the influence of hole doping on the spin and orbital correlations in transition metal oxides. The end member $\mathrm{PrV}{\mathrm{O}}_{3}$ is a Mott-Hubbard insulator, which exhibits a structural phase transition at ${T}_{\mathrm{S}}=180\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ from an orthorhombic to a monoclinic structure with space groups Pbnm and $P{2}_{1}/b$, respectively. This transition is associated with the onset of orbital ordering and strong Jahn-Teller distortions of the $\mathrm{V}{\mathrm{O}}_{6}$ octahedra. Antiferromagnetic $C$-type order with vanadium moments oriented in the $ab$ plane is observed below ${T}_{\mathrm{N}}=140\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Upon cooling, the vanadium moments induce a progressive magnetic polarization of the praseodymium sublattice, resulting in a ferrimagnetic structure with coexisting modes (${C}_{x}, {F}_{y}$) and (${F}_{x}, {C}_{y}$). In the insulating range of the $\mathrm{P}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{C}{\mathrm{a}}_{x}\mathrm{V}{\mathrm{O}}_{3}$ phase diagram, Ca doping reduces both the orbital and magnetic transition temperatures so that ${T}_{\mathrm{S}}=108\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{N}}=95\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ for $x=0.20$. The Jahn-Teller distortions and ordered vanadium moments also decrease upon doping. In a metallic sample with $x=0.30$, Jahn-Teller distortions and long-range orbital ordering are no longer observable, and the average crystal structure remains orthorhombic down to low temperature. However, broadening of some lattice Bragg reflections indicate a significant increase in lattice strain. Antiferromagnetic short-range order with a weak ordered moment of 0.14(3) ${\ensuremath{\mu}}_{\mathrm{B}}$ per vanadium atom could still be observed on the vanadium site below $T\ensuremath{\sim}60\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. We discuss these observations in terms of doping-induced spin-orbital polaron formation.

Unusual enhancement of cryogenic thermopower manifests itself around the critical point of polar order in a metal., Ferroelectrics with spontaneous electric polarization play an essential role in today’s device engineering, such as capacitors and memories. Their physical properties are further enriched by suppressing the long-range polar order, as exemplified by quantum paraelectrics with giant piezoelectric and dielectric responses at low temperatures. Likewise in metals, a polar lattice distortion has been theoretically predicted to give rise to various unusual physical properties. However, to date, a “ferroelectric”-like transition in metals has seldom been controlled, and hence, its possible impacts on transport phenomena remain unexplored. We report the discovery of anomalous enhancement of thermopower near the critical region between the polar and nonpolar metallic phases in 1T′-Mo1−xNbxTe2 with a chemically tunable polar transition. It is unveiled from the first-principles calculations and magnetotransport measurements that charge transport with a strongly energy-dependent scattering rate critically evolves toward the boundary to the nonpolar phase, resulting in large cryogenic thermopower. Such a significant influence of the structural instability on transport phenomena might arise from the fluctuating or heterogeneous polar metallic states, which would pave a novel route to improving thermoelectric efficiency.

We spectroscopically investigate a series of pyrochlore iridates ${R}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ ($R$: rare-earth and Y ions) where the metal-insulator transitions are induced by systematic bandwidth control via chemical substitutions of $R$ ions. We establish the phase diagram of ${R}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$, as endorsed by the variation of the optical conductivity spectra, in which the competing phases including paramagnetic insulator (PI), paramagnetic metal (PM), and antiferromagnetic insulator (AFI) show up as a function of bandwidth and temperature. For small $R$-ionic radius ($R=$ Y-Sm), i.e., strongly correlated region, pronounced peaks on the edge of the optical gap are discerned below the magnetic transition temperature ${T}_{\mathrm{N}}$, which is attributable to exciton and magnon sideband absorptions. It turns out that the estimated nearest-neighbor exchange interaction increases as $R$-ionic radius increases, whereas ${T}_{\mathrm{N}}$ monotonically decreases, indicating that the all-in all-out magnetic order arises from the interplay among several exchange interactions inherent to extended $5d$ orbitals on the frustrated lattice. For larger $R$-ionic radius ($R=$ Sm-Pr), i.e., relatively weakly correlated region, the optical conductivity spectra markedly change below 0.3 eV in the course of PM-AFI transition, implying that the magnetic order induces the insulating state. In particular, we have found distinct electrodynamics in the composition of $R=\phantom{\rule{4pt}{0ex}}{\mathrm{Nd}}_{0.5}{\mathrm{Pr}}_{0.5}$ which is located on the boundary of the quantum PM-AFI transition, pointing to the possible emergence of unconventional topological electronic phases related possibly to the correlated Weyl electrons.

Perovskite-type manganites exhibit various interesting phenomena arising from complex interplay among spin, charge, orbital, and lattice degrees of freedom. One such example is the keen competition between phases with different spin/charge/orbital orders. Keen competition between antiferromagnetic metal and orbital-ordered insulator is found in the slightly electron-doped regime near Mn4+ state which is stabilized by the high oxygen-pressure condition. Another one is the emergence of ferroelectricity either induced by the magnetic ordering or independently of the magnetic ordering. As the respective examples, perovskite-type YMnO3 and Sr1−xBaxMnO3 are discussed. In the YMnO3, the ferroelectric lattice distortion associated with the E-type spin order is observed for the first time. Displacement-type ferroelectricity with off-center magnetic ions is discovered for Sr0.5Ba0.5MnO3, which shows both large polarization value and strong coupling between ferroelectricity and magnetism.

Offline teaching based on high positioning accuracy of a robot arm is desired to take the place of manual teaching. In offline teaching, joint angles are calculated using a kinematic model of the robot arm. However, a nominal kinematic model does not consider the errors arising in manufacturing or assembly, not to mention the non-geometric errors arising in gear transmission, arm compliance, etc. Therefore, a method of precisely calibrating the parameters in a kinematic model is required. For this purpose, it is necessary to measure the three-dimensional (3-D) absolute position of the tip of a robot arm. In this paper, a laser tracking system is employed as the measurement apparatus. The geometric parameters in the robot kinematic model are calibrated by minimizing errors between the measured positions and the predicted ones based on the model. The residual errors caused by non-geometric parameters are further reduced by using neural networks, realizing high positioning accuracy of sub-millimeter order. To speed up the calibration process, a smaller number of measuring points is preferable. Optimal measuring points, which realize high positioning accuracy while remaining small in number, are selected using Genetic Algorithm (GA).

We investigate the variation of charge dynamics upon the metal–insulator transition for perovskite SrIr1−xSnxO3 by employing the optical spectroscopy. The Dirac semimetal of SrIrO3 turns into the a...

Organic ferroelectrics are multifunctional candidates as future organic electronics and optical devices. However, its observations in organic solids have been quite limited to well-known polymer ferroelectrics and only several low-molecular compounds until recently. Our non-covalent synthesis of the molecular compounds with hydrogen bonds between acid and base has realized a number of supramolecular ferroelectrics. These compounds display various mechanisms of ferroelectricity such as the molecular displacement and/or collective transfer of protons depending on the nature of hydrogen bonds. These principles succeeded in improving properties and would facilitate materials design toward future functional organics.

Measurements of the magnetic-field-dependent polarization of a one-dimensional organic quantum magnet suggest its ferroelectric behaviour is mediated by a spin–Peierls instability. Such behaviour could provide a promising new approach to the design of spin-driven ferroelectrics. In magnetically controllable ferroelectrics1,2,3, electric polarization is induced by charge redistribution or lattice distortions that occur to minimize the energy associated with both the magnetic order and interaction of spins with an applied magnetic field. Conventional approaches to designing materials that exploit such spin-mediated behaviour have focused mainly on developing the cycloidal spin order4,5, and thereby producing ferroelectric behaviour through the so-called antisymmetric Dzyaloshinskii–Moriya interaction6,7,8. However, engineering such spin structures is challenging. Here we suggest a different approach. Direct measurements of magnetic-field-dependent variations in the polarization of the one-dimensional organic quantum magnet, tetrathiafulvalene-p-bromanil, suggest a spin–Peierls instability has an important role in its response. Our results imply that one-dimensional quantum magnets, such as organic charge-transfer complexes, could be promising candidates in the development of magnetically controllable ferroelectric materials.

This study describes a device using pressure-sensitive electro-conductive knitting called PCK. PCK is electric conductive material made from fiber including PE 70% and SUS 30%. And it's resistance changes in the fibers according to the modification. So it can be used as a sensor of bending, stretching and pressure. This knitting when used as sensor, is inexpensive, highly flexible and air permeable. More importantly, a wearable device made of this material have the function as a sensor only by itself. So it is considered that this material can be applied as a sensor in various applications. In this paper, a Data-glove made of PCK and measurements of the device are presented. And a recognizing system using neural network that can recognize the form of human hand from the output of the Data-glove is also presented. This system attained the high rate of recognition of 5 patterns of hand operation.

We have investigated the lattice distortion coupled to the Co $3d$-spin-state ordering in thin films of perovskite ${\mathrm{LaCoO}}_{3}$ with various epitaxial strains by measurements of the magnetization, x-ray diffraction, and optical spectra. In the system with tensile strain about 0.5%, a lattice distortion characterized by the modulation vector $q=(1/6,1/6,1/6)$ emerges at 40 K, followed by a ferromagnetic ordering at 24 K. Alternatively, in systems with tensile strain exceeding 1%, the lattice distortion characterized by $q=(1/4,1/4,1/4)$ emerges at 120 K or higher, and subsequently the ferromagnetic or ferrimagnetic ordering occurs around 90 K. The evolution of infrared phonon spectra and resonant x-ray scattering at the Co $K$ edge suggests that the population change in the Co $3d$ spin state causes the strain-induced switching of spin-state ordering as well as of magnetic ordering in this canonical spin-state crossover system.

We investigate magnetotransport properties in a single crystal of pyrochore-type ${\mathrm{Nd}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$. The metallic conduction is observed on the antiferromagnetic domain walls of the all-in--all-out-type Ir $5d$ moment ordered insulating bulk state that can be finely controlled by an external magnetic field along [111]. On the other hand, an applied field along [001] induces the bulk phase transition from insulator to semimetal as a consequence of the field-induced modification of the Nd $4f$ and Ir $5d$ moment configurations. A theoretical calculation consistently describing the experimentally observed features suggests a variety of exotic topological states as functions of electron correlation and Ir $5d$ moment orders, which can be finely tuned by the choice of rare-earth ion and magnetic field, respectively.

In the course of screening for novel naturally occurring insecticides from Chinese crude drugs, the MeOH extract of the fruits of Evodia rutaecarpa Benth was found to give insecticidal activity against larvae of Drosophila melanogaster Meigen. Three alkaloids, evodiamine (1), rutaecarpine (2) and rhetsinine (3), were isolated by bioassay-guided fractionation of the extract. Insecticidal activity against larvae of D melanogaster was demonstrated; compounds 1 and 2 gave LC50 values of 0.30 and 0.28 µmol ml−1 diet respectively. Acute toxicity against adults of D melanogaster was also found; compound 2 had the most potent activity, with an LD50 value of 3.58 µg per adult. However, compound 3 had only weak activity in this study. Therefore compounds 1 and 2 were identified as insecticidal compounds from the fruits of E rutaecarpa. Compound 3 was obtained by the photoxidation of evodiamine. Investigation of the structure–activity relationship indicated the importance of the indoloquinazoline unit at the C-14 position. © 2002 Society of Chemical Industry

In the course of screening for novel naturally occurring insecticides from Chinese crude drugs, the methanolic extract of the bark of Phellodendron amurense Rupr was found to show insecticidal activity against larvae of Drosophila melanogaster Meigen. Two alkaloids, berberine (1) and palmatine (2), were isolated by bioassay-guided fractionation of the extract. Insecticidal activity against larvae of D melanogaster was demonstrated; 1 and 2 gave LC 50 values of 2.44 and 8.45 μmol ml -1 diet respectively. Acute toxicity against adult D melanogaster was also found; 1 had the more potent activity, with an LD 50 value of 19.0 μg per adult. However, 2 had weak activity in this study. Therefore 1 was identified as an insecticidal compound from the bark of P amurense Rupr. L'extrait methanolique de l'ecorce de Phellodendron amurense presente une activite insecticide contre les larves de Drosophila melanogaster Meigen. Dans cette etude, l'isolement et les activites des composes actifs sont decrits. Deux alcaloides, la berberine et la palmatine, sont isoles par un fractionnement biologique de l'extrait. La berberine est identifiee en tant que compose insecticide de l'ecorce de P. amurense.

We have investigated the dynamics of spin-state crossover (SSC) for perovskite ${\mathrm{LaCoO}}_{3}$ through optical phonons by means of infrared and inelastic x-ray spectroscopy. Upon thermally induced SSC, anomalously dispersionless Co-O bond stretching phonons coupled to the thermally excited spin state have been identified. The enhanced spin-state fluctuation irrespective of the presence of a clear charge gap suggests the emergence of complex spin-state disproportionation involving low-, intermediate-, and high-spin states due to the strong correlation among thermally activated spin states.

We studied single crystals of $\text{BaV}{}_{13}$$\text{O}{}_{18}$, in which V ions with an average valence of +2.62 ($3{d}^{2.38}$) form a quasi-fcc lattice. We found that the ground state of the stoichiometric crystal is insulating, whereas that of the off-stoichiometric crystal is metallic with a large effective mass. This metallic state can be explained by the Kondo coupling between the magnetic moment existing at the lone V ion and itinerant carriers in the V tetramers.