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  • 1
    Electronic Resource
    Electronic Resource
    Asymmetric-to-centrosymmetric structure change of molecules in squaric acid crystal: Evidence for pressure-induced change of correlated proton potentials (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5429-5435 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-pressure effects on vibrational modes have been investigated in crystals of squaric acid H2C4O4 (H2SQ) and its deuterated analog (D2SQ) which show two-dimensional networks of hydrogen bonds. Specific vibrational modes in Raman and infrared spectra were observed to anomalously disappear with the application of pressures above 30 kbar in H2SQ, but not in D2SQ, indicating that the H2SQ molecule in crystal shows the asymmetric (C1h)-to-centrosymmetric (C4h) structure change. This is possibly caused by pressure-induced deformation of the correlated proton potential essentially from the double-well to single-well type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459639
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  • 2
    Electronic Resource
    Electronic Resource
    Pressure-induced disappearance of the in-plane lattice distortion in layered cupric chloride: (C2H5NH3)2CuCl4 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1763-1766 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Effects of hydrostatic pressure on Raman scattering and electronic absorption spectra have been investigated in layered cupric chloride (C2H5NH3)2CuCl4, consisting of strongly Jahn–Teller (JT) deformed CuCl4 layers. We observed selective deactivation of the Cu–Cl stretching modes at a pressure above ∼4 GPa, and interpreted the phenomena in terms of disappearance of the in-plane lattice distortion of the CuCl4 layer. The pressure-induced structural change reduces the charge-transfer (CT)-type gap from the ligand (Cl3p) to metal (Cu3dx2−y2) sites by ∼0.4 eV, and perhaps produces the two-dimensional electronic states analogous to that of the parent compounds for the cupric superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467754
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  • 3
    Electronic Resource
    Electronic Resource
    Anomalous pressure effects on the Raman spectra in hydrogen-bonded molecular chain systems (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1813-1819 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Effects of hydrostatic pressure on the Raman spectra have been investigated for four kinds of 1,3-diketone crystals with hydrogen-bonded molecular chains. In all the crystals we studied, intense CO stretching Raman mode shows pressure-induced softening reflecting compression of the hydrogen bonds. Furthermore, application of pressure broadens the both C=O and C–O stretching modes and intensifies several specific vibrational bands. We ascribed these spectral changes to formation or growth of the kink-type defects of the hydrogen-bonded sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467760
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric phase transition and symmetry change of constituent molecules in proton–deuteron mixed crystals of squaric acid (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2244-2251 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated effects of random substitution of proton sites with deuterons on the temperature- and pressure-induced phase transitions in squaric acid crystal, which consists of ferroelectrically ordered molecular sheets of [C4O4]2−(SQ2−) skeletons and intervening protons or deuterons. In the isotopically mixed crystals (H1−xDx )2SQ, the critical temperature Tc for the dielectric phase transition was found to increase linearly with the deuterium concentration x, while the critical pressure Pc increases nonlinearly with x at 300 K. Around the pressure ∼20 kbar above Pc , the constituent SQ2− skeletons in the paraelectric phase show a symmetry change from the asymmetric (C1h ) to centrosymmetric (C4h ) form, which is likely caused by the deformation of the correlated proton (deuteron) potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460980
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  • 5
    Electronic Resource
    Electronic Resource
    Anomalous pressure effects on optical spectra of hydrogen-bonded molecular chain solids: Possible formation of kink solitons (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8507-8513 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared (IR) and visible absorbance spectra were measured as a function of hydrostatic pressure for five kinds of organic crystals composed of hydrogen-bonded molecular chains. An unconventional vibrational band is observed in the IR spectra around 1800 cm−1 commonly in these compounds and its intensity rapidly increases with pressure. We have ascribed the observed band to a proton vibration localized around kink-type defects or solitons in the hydrogen-bonded molecular chains. In accordance with the pressure-induced growth of the IR band, a new electronic absorption band appears in the visible region below the ordinary molecular excitation, suggesting a change in the electronic structures within the molecules around the soliton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462303
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  • 6
    Electronic Resource
    Electronic Resource
    LAYERED MAGNETIC MANGANITES (2000)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 30 (2000), S. 451-474 
    Details
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We review the recent progress in the study of layered magnetic manganites La2-2xSr1+2xMn2O7, which have many unique features of charge transport and magnetism inherent to the quasi-two-dimensional electronic structure. The system shows a wide variety of magnetic-field-induced phenomena due to the layered crystal and magnetic structure, such as the highly anisotropic ferromagnetic metallic ground state, the colossal magnetoresistance (CMR) effect, and the tunneling-type magnetoresistance (TMR). The charge transport properties, as well as the magnetic ones, strongly depend on the carrier-doping level and the applied pressure, which reflects the variation of the orbital-dependent occupancy of itinerant eg-like electrons. Although the layered manganite is one of a new class of CMR materials, the study of this system may also reveal some of the key issues for understanding the CMR effect in mixed-valent manganese oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.matsci.30.1.451
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  • 7
    Electronic Resource
    Electronic Resource
    Switching effect in organic charge transfer complex crystals (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2111-2113 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reproducible current switching effect has been observed in various mixed-stack organic charge transfer crystals whose ionicities are close to the neutral-ionic phase boundary. This effect appears to be related to the intrinsic nonlinear conductivity, which has recently been reported in these crystals. This switching has a reasonably large delay time and our results indicate that it is a bulk property of the crystals. Discussion is given on the possible mechanism of this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102078
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic states in lateral structures on modulation-doped heterointerfaces (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1403-1405 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic states in an AlGaAs-GaAs modulation-doped heterointerface with a lateral structure of order 10 nm are analyzed self-consistently. The structure is realized by using a fractional layer superlattice. Resonant gaps appear in the electron state band diagram because the potential cannot be expressed as a sum of the functions of two directions. The electron channel location strongly depends on which subband the electron belongs to.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101607
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  • 9
    Electronic Resource
    Electronic Resource
    Origins of colossal magnetoresistance in perovskite-type manganese oxides (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5288-5291 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phenomena of colossal magnetoresistance (MR) or magnetic field induced insulator–metal (I–M) transitions have been investigated for single crystals of perovskite-type manganese oxides with controlled carrier density and one-electron bandwidth. In addition to the canonical MR behavior near the Curie temperature, the first-order phase transition accompanying several orders of magnitude change in resistivity has been observed under an external magnetic field for many of the composition-controlled crystals as an intrinsic bulk phenomenon. It was proved by the systematic experimental investigations that the field-induced destruction of the charge-ordered state accompanying the lattice structural as well as metamagnetic transition is a major origin of such a colossal MR. Versatile MR phenomena and I–M phase diagrams in the T–H plane are presented with their interpretation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361353
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  • 10
    Electronic Resource
    Electronic Resource
    Visible luminescence from branched silicon polymers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3362-3366 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Luminescence spectra and their variation with temperature have been investigated for solid films of poly(methylphenylsilane) and its branched analogs. Introduction of branching points to the polymers enhances the broad luminescence band in the visible region while suppressing the sharp UV luminescence band due to the resonant recombination of the exciton. The intensity of the visible luminescence is observed to keep on increasing with decreasing temperature in contrast with the nearly temperature-independent intensity of the resonant luminescence. The behavior is interpreted in terms of phonon-assisted tunneling between luminescence centers and nonradiative ones. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359962
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