Quadrupolar relaxation and hopping motion of oxygen inYBa2Cu3O

Oxygen Diffusion in YBa2Cu3O7–δ Studied via 133Ba(EC)133Cs Nuclear Quadrupole Interaction

“…At present, we do not know why we see no discontinuous features at the orthorhombic-to-tetragonal phase transition near 973 K. Possibly, the fact that the spectroscopy is actually performed on 133 Cs, obtained by electron capture from 133 Ba, is responsible for this phenomenon. A similar argument was given by Singh et al [2] for their studies using in In as a probe. Contrary to their experiment, however, we see an unbroadened, static signal at low temperatures, which progressively broadens at intermediate temperatures, and enters the motional narrowing regime at very high temperatures.…”

“…Contrary to their experiment, however, we see an unbroadened, static signal at low temperatures, which progressively broadens at intermediate temperatures, and enters the motional narrowing regime at very high temperatures. We have no explanation for the fact that the lu In spectra of Singh et al [2] showed massive linebroadening at the lowest temperature and exhibited motional narrowing right away from 250 K upwards. Therefore, we can not identify their activation energy of 33(4) meV for oxygen jumps with any of our derived quantities.…”

“…Therefore, we can not identify their activation energy of 33(4) meV for oxygen jumps with any of our derived quantities. Probably, as outlined by Singh et al [2], the near neighbour oxygen 0(4) to Cu(l) is not mobile for In on a Cu(l) site.…”

“…On the contrary, local techniques like hyperfine techniques thus far either addressed static aspects of the Cu-environment [1] or were carried out on samples doped with impurity probes [2], In this paper we report on the first measurements of the 133 Ba(EC) 133 Cs nuclear quadrupole interaction (NQI) in YBa 2 Cu 3 0 7 _ (5 by time differential perturbed angular correlation (TDPAC). We deduce hopping rates for the mobile oxygen as well as energy barriers representative for the elementary jump process.…”

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“…The specific advantages of nuclear spectroscopic techniques, which use radioactive isotopes to study HTS are still far from being exploited. Previous studies using Mössbauer Spectroscopy [8], Perturbed Angular Correlations (PAC) [9] and Emission Channeling (EC) [10] were limited by the small number of suitable probe elements and by the poor quality of the available samples of superconductors.…”