Cluster spin glass phase and charge stripe fluctuations in the high- Tc superconductor La 2− xSr xCuO 4

Abstract

A rise of the acoustic absorption in correspondence with the freezing of the Cu 2+ spins into the cluster spin glass state has been identified with the fluctuations of the walls between the antiferromagnetic spin clusters, pinned by the Sr dopants. The depinning of the stripes is identified with an additional absorption maximum around 80 K , whose intensity and effective activation energy (identified with the pinning barrier) exhibit a dependence on doping consistent with pinning and stripe–strain interaction being mediated by the octahedral tilts.