Anomalous behavior around 220 K in optimal doped investigated by Sr substitution

Much interest has been paid to the origination of anomalous behavior around 220 K in optimal doped YBa 2 Cu 3 O 7 − δ (Y123). In mechanical spectroscopy, an internal friction peak (labeled as P 1 ) was observed in this temperature range. Following a previous internal friction study of Sr substituted Y123, Raman spectroscopy was used to evaluate the structural change during Sr substitution. A clear change of Raman phonon at 340 cm−1, which corresponds to the vibrations of the oxygen atoms in two adjacent planes out of phase and out of the plane, was observed with Sr substitution. Then a correlation between internal friction P 1 peak and Raman spectrum supports the close relationship between P 1 with the CuO2 plane rather than CuOx chains. Furthermore, the possible relationship of P 1 with the dynamical stripe scenario was discussed.