Neutron scattering investigation of superconducting ceramics Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3Ox

The main purpose of this report is to present a short description of the experiment and of the preliminary results obtained from the slow neutron scattering measurements on a high temperature superconducting material performed on the time of flight spectrometer NEAT of BENSC. In this study we have used cold neutrons with λ =5.1 A and a resolution ΔE = 98 μeV (full width at the half maximum of the elastic line of a vanadium sample). The scattering spectra were taken with 140 detectors in a large angular range 15. 41 angle ≤ Θ ≤ 134.5 angle. All runs were measured within the temperature range 100 K - 300 K. The final data are obtained at 28 scattering angles as a function of the energy transfer for 4 temperatures (100 K, 110 K, 130 K and 300 K). The preliminary data are presented for 3 temperatures, at 300 K, 110 K and 100 K corresponding to the normal, transition and to the superconducting state, respectively, and are analyzed in terms of the generalized phonon frequency distribution (GFD). The preliminary conclusions could be summarised as follows: - GFD is obtained by averaging over the final scattering vectors within a large range of scattering angles (Bredov and Oskotskij method) at 3 temperatures; - Well resolved peaks at 5.57 meV, 10.43 meV, 19.38 meV, 29.68 meV, 67.42 meV and 109.48 meV were observed in GFD at 300 K, peaks at 5.21 meV, 10.39 meV, 24.51 meV, 45.42 meV, 59.5 meV and 69.29 meV at 110 K and 5.7 meV, 10.26 meV, 20.46 meV and 44.44 meV at 100 K; - The first three excitations including the first soft mode at 5.2 ± 0.5 meV for all temperatures during the transition from normal to the superconducting state are present; - A strong temperature dependence of the high energy limit of the frequency spectra was evidenced. (authors)