Investigation of the cluster spin-glass transition in La2-xSrxCuO4 by means of anelastic spectroscopy

A step-like increase of the acoustic absorption (Q-1) is found in La2-xSrxCuO4 (x = 0.019, 0.025, 0.032 and 0.064) below the temperature (Tg) at which NQR and ?SR measurements evidenced the formation of a cluster spin-glass (CSG) state. The sharp maxima appearing in the 139La NQR and ?SR relaxation rates indicate the slowing down of antiferromagnetic fluctuations below the measuring frequency (107-108 Hz in those experiments). The acoustic absorption does not appear to be due to the freezing of magnetic fluctuations, for which one expects a narrow peak; rather, it is attributed to the size change of the antiferromagnetically correlated clusters, produced through magnetoelastic coupling by the vibration stress.