College of Letters & Science

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The College of Letters and Science, the largest center for learning, teaching and research at Montana State University, offers students an excellent liberal arts and sciences education in nearly 50 majors, 25 minors and over 25 graduate degrees within the four areas of the humanities, natural sciences, mathematics and social sciences.

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1985 - 19883

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Author: search.filters.author.Drumheller, John E.Subject: search.filters.subject.Physics

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    Dielectric measurements of the proton-glass state in Rb0.65(NH4)0.35H2AsO4
    (1988-09) Trybuła, Z.; Schmidt, V. Hugo; Drumheller, John E.; He, Di; Li, Zhouning
    Dielectric measurements of the Rb1−x/emph>(NH4)xH2AsO4 (x=0.35) mixed crystals in the a and c tetragonal directions in the temperature range from 3 to 300 K are reported. Below Tg a dielectric dispersion of ε’(T) and ε’’(T) in the applied frequency range from 1 Hz to 30 kHz was observed. A small anisotropy of the proton-glass transition temperature Tg was detected, but we did not find the large anisotropy reported by J. Kim, N. Kim, and K. Lee [J. Phys. C 21, L-663 (1988)].
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    EPR investigation of Cu2+ tetramers in ferroelectric CsH2PO4
    (1985-07) Waplak, S.; Schmidt, V. Hugo; Drumheller, John E.
    EPR study of CsH2PO4 (CDP) single crystals with 0.005 mol % of Cu2+ at room temperature reveals isolated Cu2+ (S=(1/2)) complexes with four ligand coordination and spin Hamiltonian parameters gpara=2.2575, g⊥=2.1866, Apara=30 G, and A⊥=27 G. At temperatures below 250 K the spectra were observed to have fine structure and are described as arising from a Cu2+ tetramer with effective spin S=2 and spin Hamiltonian parameters D=0.181 cm−1, E=-0.081 cm−1, a=0.001 cm−1, b=0, and c=-0.021 cm−1. Also reported are transitions within the S=1 multiplet of the tetramer, and a microscopic model of superexchange interaction has been used to evaluate the parameters Dx=0.543 cm−1 and Ex=-0.159 cm−1. A tetramer model as well as a temperature dependence of the ratio of tetramer–to–single-ion intensity is presented.
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    EPR determination of three-dimensional correlations below the ferroelectric phase transition in pseudo-one-dimensional CsH2PO4:Cu2+
    (1986-11) Waplak, S.; Schmidt, V. Hugo; Drumheller, John E.
    The polarization fluctuations of ferroelectric CsH2PO4 above Tc are generally classified as a quasi-one-dimensional phenomenon. The temperature dependence of the EPR line splitting of the S=1 state of the Cu2+ tetramer, however, exhibits a critical exponent below Tc of β=0.5 indicating that the correlations associated with the order parameter are three dimensional below Tc.
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