Normal-state anomalous behaviours studied by the internal friction of YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-δ</inf>

Abstract

The internal friction of Ca partially substituted Y 1-x Ca x Ba 2 Cu 3 O 7-δ ceramics was measured using the vibrating reed method from liquid-nitrogen temperature to room temperature at kilohertz frequency. There are two thermally activated relaxation peaks (called P1 and P2 at 95 K and 120 K, respectively). The intensity of P1 almost remains unchanged with Ca substitution, while that of P2 decreases. Another internal friction peak appears around 220 K (called P3). With the increase of Ca content, the intensity of P3 decreases and the peak position shifts toward low temperature. We also have observed that Zn substitution affects P3 much less and Fe substitution seems to result in another contribution to the internal friction around 250 K. We expect that the P3 peak originates from a charge-carrier crossover and possibly has some relationship with the occurrence of the dynamic stripe at low temperature.