Room temperature crystalline structures of La2-xSrxCuO4 samples with uncommonly high hole concentrations (p) up to p=0.4, annealed under 1 and 100 bars of oxygen pressure have been analyzed by X-ray diffraction. Results show that the x=0 sample with p=0.09 and superconducting below 20K is orthorhombic at room temperature. The orthorhombic distortion at 300K decreases with increasing x and becomes tetragonal when x reaches 0.08. This orthorhombic-to-tetragonal phase transformation is consistent with previous work. Samples with x≥0.28 and p≥0.31 remain tetragonal but are nonsuperconducting down to 5K. Lattice dimension anomalies have also been observed and are correlated with the sudden appearance of oxygen vacancies, as seen by the hole concentration measurements. Initially, the value of the lattice dimension a decreases and c increases monotonically with increasing x. A sudden increase in a and decrease in c begins when x reaches 0.28 for samples prepared under 1 bar of oxygen indicating a sudden loss of oxygen from the structure. This sudden reversal in lattice dimensions a and c is not present in samples annealed under 100 bars of oxygen pressure suggesting essentially no oxygen vacancies. The increase in c with x of the La2-xSrxCuO4 samples with no oxygen vacancies can be attributed mainly to the result of substituting smaller La+3 ions by larger Sr+2 ions. A study of the variation of c with the hole concentration reveals that the c lattice dimension drops sharply with no change in the hole concentration when oxygen is continuously removed from the lattice caused by an increase of the Sr content in La2-xSrxCuO4.

An ordered oxygen-deficient tetragonal perovskite compound La1.67Sr0.33Cu205 has been synthesized by solid state reaction. X-ray powder diffraction was used to characterize the material. Unit cell parameters least-squares refined from non-overlapping diffraction peaks are a = 10.8696(9)Å, c = 3.8612(6)Å and V = 456.2(1)Å3. X-ray powder data have been obtained for the experimentally observed peak positions corrected for systematic errors, the relative intensities, values of dexp and the Miller indices of both resolved and overlapping reflections. The experimental diffraction pattern was compared to computer simulated patterns calculated from the neutron crystal structure parameters and the non-oxygen-deficient LaCuO3 compound. The figure of merit is F30 = 33.8 (0.018, 48).

Resonant elastic X-ray scattering (RXS) at the erbium absorption edge was investigated in the orbital-ordered compound ErVO3. An RXS signal resonating near the Er L3-edge was clearly observed at (1 0 0). Using this signal, we studied the relation between the anisotropy of the Er 5d orbital and the V 3d orbital ordering because the covalency between the Er 5d and V 3d orbitals is expected to stabilize the C-type orbital ordering of the V 3d electrons.

The orbital ordering in perovskite-type vanadium oxides, RVO3 (R: rare earth), has been investigated by resonant X-ray scattering (RXS) near the V K-edge energy. The G-type orbital order, C-type orbital order and orbital disorder phases are elucidated on the basis of the azimuthal-angle and polarization dependence of the RXS signal reflecting the orbital ordering.

The life cycle of Gnathostoma nipponicum was examined by field survey and by experimental infection of animals with the larvae. Naturally infected larval G. nipponicum were found in loaches, catfish, and snakes. Experimentally, loaches, killifishes, frogs, salamanders, mice, and rats were successfully infected with the early third-stage larvae of G. nipponicum obtained from copepods (the first intermediate host), whereas snakes, quails, and weasels were not. Frogs, snakes, quails, and rats were experimentally infected with the advanced third-stage larvae (AdL3) from loaches. These results reveal that some species of fishes, amphibians and mammals can act as the second intermediate host and that some species of reptiles, birds and mammals can act as a paratenic host. The life cycle was completed in weasels, the definitive host, which were infected with AdL3 from loaches and started to evacuate eggs of G. nipponicum in faeces on days 65–90 postinfection.

In complex transition-metal oxides, the interactions between the electronic spins, charges, and orbitals produce a rich variety of electronic phases. The competition and/or cooperation among these correlated-electron phases can lead to the emergence of surprising electronic phenomena and functionalities and form the basis for a new type of electronics.

We report resonant x-ray scattering studies of charge and orbital order in Prl−xCaxMnO3 with x=0.4 and 0.5. Below the ordering temperature, To=245 K, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, TN. High resolution measurements reveal, however, that long range orbital order is never achieved. Rather, an orbital domain state is formed. Above To, the charge order fluctuations are more highly correlated than the orbital fluctuations. We conclude that the charge order drives the orbital order at the transition.

A systematic study is presented for structural characterization and physical properties of two kinds of perovskite oxide superlattices composed of ferromagnetic (FM) and antiferromagnetic (AF) layers. Spin ordering structures is modulated in FM La0.6Sr0.4MnO3/G-type AF La0.6Sr0.4FeO3 superlattices, whereas, ordering structures both in spin and orbital are modulated in La0.6Sr0.4MnO3/A-type AF La0.45Sr0.55MnO3 along the growth directions. Large magnetoresistance subsists down to low temperature in La0.6Sr0.4MnO3/La0.6Sr0.4 Fe3 (F/G) superlattices as a result of recovery of ferromagnetism, which is once suppressed by spin frustration at the interface between FM and G-type AF layers. In contrast, the constituent layers in the La0.6Sr0.4MnO3/La0.45Sr0.55MnO3 (F/A) superlattices appear to keep their ground states due to the absence of spin frustration at the interface. Magnetoresistance is pronounced in this type of superlattices at low temperatures when the AF layer is very thin, indicating restoration of the electronic coupling between the neighboring FM layers which are otherwise decoupled by intervening A-type AF spin ordering and dx2−y2 orbital ordering in La0.45Sr0.55MnO3 layers.

We have studied the fc-dependent electronic structure of the layered colossal magnetoresistive manganite La1.2Sr1.8Mn2O7 using high-resolution angle-resolved photoemission spectroscopy. We found dispersive energy bands as a function of the crystal momentum k near the Fermi level (EF). We have also performed local spin density approximation (LSDA)+U band-structure calculations on the current system. The overall experimental dispersion relation is basically in agreement with the band-structure calculations yet close to EF there is a significant deviation from the predicted dispersions. Instead of clear Fermi-surface (FS) crossings, we observe a depression of the features as the FS is approached as if there is a “pseudo” gap in the excitation spectrum. The pseudogap continuously opens with temperature and does not show further significant opening above Tc, corresponding to the metal-insulator transition. Those unusual aspects of the spectra has been discussed from the viewpoint of the strong electron-lattice coupling model.

Anisotropie charge transport and magnetic properties have been investigated for single crystals of the layered manganite, La2–2xMn2O7 (0.3≤x≤0.5). Remarkable variations in the magnetic structure as well as in the charge-transport properties are observed with changing doping-level x. A crystal with x=0.3 behaves like a 2-dimensional ferromagnetic metal in the temperature region between ∼90 K and ∼270 K, and shows the interplane tunneling magnetoresistance at lower temperatures. These characteristic charge-transport properties are attributed to the interplane magnetic coupling between the adjacent MnO2 bilayers, and are strongly affected by the application of pressure as well as low magnetic fields through the change in magnetic structure. With increase of the carrier concentration toward x=0.5, the charge-ordered phase is stabilized and dominates the charge transport and magnetic properties.

We have performed X-ray absorption (XAS) and angle-resolved photoemission (ARPES) on single crystals of both the layered and cubic colossal magnetoresistive manganites to determine the electronic structure and the relevant energy scales in the problem: the intra-atomic exchange energy J (∼ 2.7 eV), the Jahn-Teller energy gain EJ-T (<.25 eV), the one-electron bandwidth W (>3 eV for layered compounds) and the lattice relaxation or polaron binding energy EB (.65 eV ferromagnetic phase and.8 eV paramagnetic phase). Lattice polarons are deemed important especially in the paramagnetic but also to a degree in the ferromagnetic phase. Due to the energy scale mismatch, the Jahn-Teller effect is unlikely to be the cause for these lattice polarons, at least for the layered samples.

We have investigated electronic transport and magnetic properties of perovskite-type Nd1-xSrxMnO3 crystals with change of controlled hole-doping level (0.30≤x≤0.80). The electronic phase diagram of Nd1-xSrxMnO3 was obtained by systematic measurements of magnetization (magnetic structure), resistivity, and lattice parameter. We have also studied the anisotropie transport properties of x=0.50 and 0.55 crystals with different magnetic structures: CE-type antiferromagnetic (AF) structure for x=0.50 and A-type layered AF one for x=0.55. In the case of the x=0.55 crystal, the metallic behavior was observed within the ferromagnetic (F) layers, while along the AF-coupling direction the crystal remains insulating over the whole temperature region. The observed large anisotropy is due to the magnetic as well as orbital-ordering induced confinement of the spin-polarized carriers within the F sheets. The nearly isotropie transport behavior has been confirmed for the CE-type AF charge-ordered state in the x=0.50 crystal.

In this work we report a study of the photoinduced insulator-to-metal transition in manganese oxide perovskites of the formula Pr1-xCaxMnO3. The transition is closely related to the magnetic field induced insulator-to-metal transition (CMR effect) observed in these materials. It is accompanied by a dramatic change in the magnetic properties and lattice structure: the material changes from an insulating charge-ordered canted antiferromagnet to a ferromagnetic metal. We present an investigation of the transport and structural properties of these materials over the course of the transition (which usually takes about an hour to complete). The current-voltage characteristics exhibited by the material during the transition are highly nonlinear, indicating a large inhomogeneity of the transitional state. Possible practical applications of this novel type of transition are briefly discussed. We also report a high-resolution x-ray diffraction study of the charge-ordering in these materials. The temperature dependent charge ordering structure observed in these compounds is more complex than previously reported.

We have investigated the magnetic anisotropies of doped manganite materials in epitaxial thin film and single crystal form. Structural characterization, including x-ray diffraction, Rudierford backscattering spectroscopy and atomic force misocroscopy, indicate that our epitaxial films arc single crystalline and have excellent crystallinity. Since lattice distortions greatly affect the magnetic and transport properties of this family of materials, it is not surprising to find the profound effect of strain in films due to the lattice mismatch between the substrate and film. Magnetic anisotropy results of single crystals, subject to no external stress, is compared to those of epitaxial films.

We have discovered 24 K-superconductivity in a family of compounds Ln2−xCexCuO4−y (Ln=Pr, Nd, Sm). Novel feature of the superconductivity in these family of compounds is that superconductivity is produced by electron-doping in sharp contrast with high-Tc cuprates discovered so far. The effect of doping on physical properties particularly the elecronic phase diagram and transport coefficients which indicate symmetry in many respects between electron- and hole- doping is described.