Scholarly Work - Physics
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Item Comment on “dielectric study of the ferroelectric transition of KH2PO4”(1976-08) Western, Arthur B.; Schmidt, V. HugoWe reanalyze a.c. dielectric data taken by Eberhard and Horn for KH2PO4 near Tc, and obtain a much lower value of the critical bias field, near 300 V/cm in accord with results found by other workers.Item One-dimensional model for cooperative hydrogen motion in ferroelectric crystals(1974-01) Schmidt, V. HugoThe static and dynamic behavior is examined for “Takagi groups” in double-minimum potential wells containing protons (or deuterons) coupled by harmonic forces. Predictions of this model are compared with observed isotope effects on domain wall mobility and dielectric relaxation in KH2PO4. The model predicts effects previously attributed to tunneling.Item Hydrostatic optical cell with simple window structure for low temperature and hydrostatic pressure up to 5 kilobars(1978) Yamada, Masayoshi; Schmidt, V. HugoA compact gas high‐pressure cell with four windows for optical studies of phase transitions at low temperature and hydrostaticpressure up to 5 kilobars has been made. Techniques for sealing window components are discussedItem Dielectric Properties of Lithium Hydrazinium Sulfate.(1971-12) Schmidt, V. Hugo; Drumheller, John E.; Howell, Francis L.The dc conductivity and ac dielectric susceptibility of normal and deuterated lithium hydrazinium sulfate have been measured over a wide temperature range at frequencies up to 9.33 GHz. Over a very large temperature and frequency range the real and imaginary parts of the susceptibility are very large (up to ε′≃ε''≃106) and vary with frequency somewhat as f−12. This unusual behavior is shown to result form the nearly one-dimensional protonic conductivity and its extreme sensitivity to barriers caused by local structural defects. Etching studies indicate that the crystal is not ferroelectric, implying that the apparent hysteresis loops result from saturation of the ac conduction.Item Ferroelectricity Experiment for Advanced Laboratory(American Institute of Physics, 1969-04) Schmidt, V. HugoAn experiment suitable for a junior or senior physics laboratory is described, in which the spontaneous polarization and coercive field for Rochelle salt are measured from the ferroelectric hysteresis loops, over the temperature range −18° to +24°C in which this crystal is ferroelectric. The suitability of triglycine sulfate for this experiment is discussed. The apparatus is also useful in demonstrating the relation of capacitance to electrode geometry, and in determining dielectric constants.Item Random Motion of Deuterons in KD2PO4(American Physical Society, 1969-04) Schmidt, V. Hugo; Uehling, Edwin A.Magnetic resonance studies of the deuteron in KD2PO4 have been conducted which show the existence of deuteron jumping between and within hydrogen bonds. The experimental results help to explain electrical conductivity and ferroelectric phenomena in crystals of this type. Pulse magnetic resonance experiments show that the lifetime TXY against deuteron jumping between X- and Y-oriented hydrogen bonds is 15 msec at 70°C with a jump activation energy of approximately 0.58 ev. The c-axis electrical conductivity of KD2PO4 is found to have the same activation energy, with a value of 1.16×10−10 (ohmcm)−1 at 25°C. The Δm=1(P1) and Δm=2(P2) deuteron spin-lattice relaxation transition probabilities due to X−Y jumps have been calculated from the known values of TXY and the electric field gradient tensors at X and Y deuteron sites. Their magnitudes and the dependences of these magnitudes on magnetic field, temperature, and orientation are in good agreement with experiment. Further measurements of P1 and P2 separately give a component of transition probability proportional to exp(0.078 ev/kT) and independent of magnetic field. The orientation dependences of P1 and P2 for this component indicate quadrupolar relaxation due to deuteron jumps along hydrogen bonds, with a jump time of order 10−11 sec at 215°K. The existence of intrabond jumps governed by an activation energy is shown to be consistent with the Slater theory of KH2PO4 as modified by Takagi.