Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 23 for “"structural phase transition"”.
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Synthesis And Characterization Of Transition Metal Arsenide Nanocrystals And The Metastability And Magneto-Structural Phase Transition Behavior Of Mnas Nanocrystals
… study focuses on (1) probing the magneto-structural phase transformation in nanoscale MnAs; (2) evaluation of the size-dependent phase stability of type-B MnAs (prepared by rapid injection); and (3) developing a general synthetic method for transition metal arsenide nanoparticles.</p> …
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Investigation of Frustrated Quasi-One-Dimensional Quantum Spin-Chain Materials
… physical characterization of the magnetic and structural properties of CuAs2O4 was carried out. Under the effect of hydrostatic pressure, CuAs2O4 was found to undergo a structural phase transition at 9 GPa to a new spin-chain structure. The structural phase transition is accompanied by a severe …
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Muonium in C₆₀ fullerites : studies of structural and electronic properties
… the molecular dynamics and is used to study the structural phase transition of solid C₆₀ near 260K. Only endohedral muonium is observed in the alkali-metal-doped fullerites K₄C₆₀, K₆C₆₀, and Rb₆C₆₀. From its coherent spin precession, we find all three to be semiconductors with small gaps on the …
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Imaging magnetic order in magneto-structural phases of Mn3O4
… Mn3O4 is known to have two distinct phases below the Neel temperature that differ in both structure and magnetic order, including a tetragonal phase with disordered spins, and at lower temperatures, an orthorhombic phase exhibiting long-range commensurate magnetic order. Using a …
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A backscattering ion channeling study of the lattice site location of the constituents of two systems
… in the near surface region is used to observe a structural phase transition in the alloy from the zinc blende structure to a diamond structure. In the second system the extent of antimony segregation to the [111] silicon - silicon dioxide interface was first determined. Channeling scans were made …
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Synthesis and Coordination of the Arylazo Ligands 1-(2-pyridylazo)-2-phenanthrol and 1-(8-quinolynazo)-2-phenanthrol
… twelve new complexes that feature many different structural, mag- netic, and electronic properties. Chapter one deals with the aspects of materials chemistry which are pertinent to the material presented in this thesis. This includes inorganic chemistry, mag- netism, luminescence, and redox active …
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Exploring the pressure- and magnetic-field-induced phases of orbital-ordering KCuF3 and single molecule magnet Mn12-acetate: Crystal growth and Raman scattering studies
… techniques are used to probe the novel phases and properties of the orbital ordering material KCuF3 and the single molecule magnet Mn12-acetate as functions of temperature, applied pressure, and applied magnetic field. Single crystal samples of KCuF3, Mn12-acetate, 1T-TiSe2, and Bi2Se3 …
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Vibrational and thermodynamic properties of ferrocene
… to account for these effects. Fc undergoes a structural phase transition (T l63.9K for Fc, T = 203.7K for deuterated Fc). The large shift o 0 in T for deuterated Fc can be attributed to a change in the molecular o barrier to rotation of the CSHS rings about the S-fold symmetry axis. Solutions …
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Experimental observations on some reduced-oxygen Chevrel-phase compounds
… procedure for removing oxygen from the Chevrel phase compounds SnMo6Sg, PbMo6Sg, and Cu1.gMo6Sg. Measurements of the temperature dependence of the magnetic susceptibility have been made on these gettered Chevrel compounds, and comparisons have been made between the Pauli susceptibility of …
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X-ray thermal diffuse scattering and its studies of lattice dynamics
… changes when temperature is lowered towards a structural phase transition at ~ 170 K. A TDS experiment was carried out to verify this prediction, yet analysis of the data showed that it was incorrect. In another major project, a new experimental approach was proposed to allow extraction of …
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Low Temperature Single-Crystal X-ray Diffraction on A(1-x)A'xMnO3 (A=La,Eu and A'=Ba,Sr)
… their structures, that are: the analysis of the structural behavior (and its correlation to magnetic and electronic properties) of rhombohedral La0.815Ba0.185MnO3 and orthorhombic La0.89Sr0.11MnO3 in dependence on temperature, the studies of the monoclinic symmetry of La0.815Ba0.185MnO3 at T=160K …
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X-ray scattering studies of strongly correlated materials: orbital ordering in KCuF3 and stripe-like domain structures in BiFeO3 epitaxial thin films
… on KCuF3 have revealed a previously unidentified structural phase transition at T = 50 K, involving GdFeO3 like rotations of the CuF6 octahedra. These rotations are quasi-ordered and exhibit glassy hysteresis, but serve to stabilize the Neel state at T = 39 K. Based on these observations, we have …
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Topics in the theory of semiconductors: I. Novel semiconductors II. Uniaxial stress dependence of deep impurities
… band gap of Ge necessarily make deep-to-shallow transitions as the Sn concentration increases and some impurities have false valences. Chapter 2: The electronic energy band structure and deep substitutional impurity levels for InN and the alloys Inl_xGaxN and Inl_xA£xN are predicted with a …
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Photoinduced phase transitions and irreversible dynamics studied with single-shot spectroscopy
… It was then applied to investigate photoinduced phase transitions in semimetals and manganites. The dual-echelon single-shot instrument was developed, and noise sources, experimental artifacts, and the fundamental limits of the single-shot technique were explored. In this thesis, advances in the …
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Dynamics of lattice vibrations, molecular rotations and spins studied by terahertz spectroscopy
… permanent dipoles of a thermal ensemble of gas-phase molecules. Multiple pathways that lead to the nonlinear responses are mapped out in the 2D THz rotational spectrum, which allows the detailed study of the nonlinear THz field-dipole interactions with resolution of each rotational level. We …
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Novel phase and phase transition behavior of a superionic conductor observed on the nanoscale
… the ionic structure, vacancy ordering, phase transitions, and ion transport in a prototypical fast-ion conductor, copper selenide. Major objectives of my work were to elucidate i) the nature of the structural phase transition by which copper selenide becomes a superionic phase and ii) …
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Superconductivity in oxygen doped iron telluride by molecular beam epitaxy
… film quickly go from the initial polycrystalline phase to highly crystalline in just a few unit cells. We studied oxygen doping to the iron telluride thin films and the resultant superconductivity. We characterized the sample with AFM, XRD, transport, and STEM-EELS, and we found that interfacial …
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High pressure studies of superconductivity and anomalous normal states in novel quantum materials
… quantum critical point but also to enter novel phases that cannot usually be found in any materials at ambient conditions. Sb (Chapter 4): High-pressure phase Sb-II exhibits a novel incommensurate host-guest structure, giving rise to exotic sliding mode between host and guest chain. In …
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Caloric effects in ferroic materials
… intrinsic caloric effect near its ferromagnetic transition is small (-1.2 J kg−1 K−1 T−1 ) [1]. Moya et al. have discovered that LCMO thin films grown on BaTiO3 (BTO) substrates can produce extrinsic magnetocaloric effects as large as -9 J kg−1 K−1 T−1, driven by a structural phase transition in …
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First principles quantum Monte Carlo study of correlated electronic systems
… systems to study the electron correlations in transition metal oxides (vanadium dioxide) and low dimensional electronic systems (graphene and graphene-like two dimensional systems). Vanadium dioxide (VO2) is a paradigmatic example of a strongly correlated system that undergoes a metal-insulator …
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