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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Relaxor behavior in manganites (invited) (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6857-6862 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impurity (Cr3+)-doping effect on the stability of charge and orbital ordering has been systematically investigated for Nd1/2Ca1/2Mn1−yCryO3 crystals by measurements of magnetotransport and x-ray diffraction. The random field in terms of eg orbital deficiencies on the Cr sites drives the charge and orbital correlations to dynamical and short range, which is most relevant to the high-resistive state exhibiting colossal magnetoresistance. In the Cr-doped manganite, we can observe the coexistence of ferromagnetic–metallic and charge–orbital ordered phases, their spatial distributions, diffuse x-ray scattering, magnetic-field annealing, and the aging effect on the magnetic and electric properties, etc. These phenomena are reminiscent of those of relaxor ferroelectrics composed of ferroelectric clusters embedded in a paraelectric matrix. We propose that the mixed-valent manganite can be viewed as a "magneto- and electrorelaxor." © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362644
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Electron effective-mass modulation transistor (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 2171-2173 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new current-controlling structure is proposed that uses a fractional layer superlattice. The gate changes the coupling between the electrons and the superlattice. Since the current changes through the quantum mechanical interference resulting from the multiple scatterings by the periodic potentials, it needs no electron redistribution time. Therefore, a very fast response time is expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345558
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  • 9
    Electronic Resource
    Electronic Resource
    GaAs tetrahedral quantum dot structures fabricated using selective area metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2018-2020 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New GaAs quantum dot structures, called tetrahedral quantum dots (TQDs), are proposed to make a zero-dimensional electron-hole system. The TQDs are surrounded by crystallographic facets fabricated using selective area metalorganic chemical vapor deposition (MOCVD) on (111)B GaAs substrates. The calculated energy sublevel structures of zero-dimensional electrons in a GaAs TQD show large quantum size effects, because electrons are confined three dimensionally. GaAs and AlGaAs tetrahedral facet structures on (111)B GaAs substrates partially etched into a triangular shape were grown using MOCVD. Tetrahedral growth with {110} facets occurs in the triangular areas. The cathodoluminescence intensity map for GaAs tetrahedrons buried in AlGaAs shows the tetrahedral dot array.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105026
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  • 10
    Electronic Resource
    Electronic Resource
    Mobility modulation on a modulation-doped structure with an AlAs/GaAs fractional layer superlattice (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 804-806 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mobility modulation effect of AlAs/GaAs fractional layer superlattices in an AlGaAs/GaAs modulation-doped structure, which is used for quantum wire and electron wave interference transistors, is investigated by measuring their sheet electron concentration (ns). The ns obtained by the Shubnikov–de Haas oscillation is the number of high-mobility electrons. On the other hand, the ns calculated from structural parameters is the total number of the high- and low-mobility electrons. The relationship between the electron mobility and ns is found to be μ∝(ns − nc)γ, where γ=1 and nc=5.9×1011 cm−2. The mobility modulation part in the transconductance exceeds the electron concentration modulation part by a factor of 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103426
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