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 Tricritical point and tricritical exponent δ in KH2PO4(1978-01) Schmidt, V. Hugo; Western, Arthur B.; Baker, A. G.; Bacon, Charles R.Static dielectric results for a KH2PO4 crystal at pressures of 0, 2, and 2. 4 kbar are analyzed in terms of a Landau free energy expansion using the “isopol” technique. The measured exponent δ at 2. 4 kbar is consistent with the mean-field tricritical value of 5. This result and the Landau parameter values indicate a tricritical point near 2. 4 kbar.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 Exact solution in the discrete case for solitons propagating in a chain of harmonically coupled particles lying in double-minimum potential wells(1979-12) Schmidt, V. HugoSolitons of the form xn=x0tanh(ωt−kna) can propagate in a chain of harmonically coupled particles in the discrete case if the potential −1/2Axn^2+1/4Bxn^4 giving such solitions in the continuum limit is suitably modified. This modified potential is expressible in closed form, and its shape is a function of ω and k. For large ω the maximum at xn=0 becomes a minimum, giving a triple-minimum potential. Potential shapes and particle positions are illustrated for various (ω,k) combinations. The total energy and its kinetic, potential, and spring energy constituents are also expressible in closed form. In the continuum limit the total energy has the form E=(m0cS^2)/(1−v^2/cS^2)^1/2, where m0 is the soliton effective mass, v is the soliton speed, and cS is the speed of sound in the mass-spring chain.Item Spin-Lattice Relaxation of Al^{27} in Thulium Aluminum Garnet(1973-05) Trontelj, Z.; Schmidt, V. HugoThe Al27 spin-lattice relaxation time T1 has been measured between 127 and 425 °K at 8 and 14 MHz for the aluminum a and d sites in thulium aluminum garnet. Both sites exhibit T1 dips at 275 °K which are attributed to Al27-Tm169 cross relaxation. Below 190 °K the a-site T1 magnitudes and approximately ω−2 frequency dependence are explained by magnetic field fluctuations caused by the Tm3+ ion making transitions between its two lowest crystal-field levels with a correlation time near 4 × 10−12 sec.Item Tricritical Point in KH_{2} PO_{4}.(1976-11) Schmidt, V. Hugo; Western, Arthur B.; Baker, A. G.