Kimball, Clyde W.
M.S. (Master of Science)
Department of Physics
Temperature-dependent Mossbauer measurements have been carried out on the high T[sub c] oxide superconductor (La₁.₈₅Sr₀.₁₅) CuO₄ (T[sub c] = 37 K) doped with tin. Using the 23.88 keV Mossbauer resonance at ¹¹⁹Sn, the valency state of tin ions in the superconductor has been characterized and hyperfine interactions studied. The temperature dependence of the mean-squared displacement shows phonon softening near 75 and 170 K. Above 180 K the data fit to a harmonic model with 0[sub D] ~ 403K; between 77 and 160 K, 0[sub D] = 383K; and below 77 K, 0[sub D] is temperature dependent. Below 250 K, the temperature dependence of the shift indicates that, in addition to a temperature dependent 0[sub D], there are electronic changes characteristic of a phase transformation. The valency of tin is found to be 4+.
Giapintzakis, John, "A mossbauer study of phonon and electron anomalies in perovskite superconductor La₁.₈₅Sr.₁₅Cu.₉₅Sn.₀₅O₄" (1987). Graduate Research Theses & Dissertations. 414.
Northern Illinois University
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