Anelastic spectroscopy measurements of nanoscale charge and magnetic structures in cuprates and manganites

Many perovskites and perovskite related materials exhibit electronic phase separation phenomena at nanometer scales, which are thought to concur to important electric and magnetic properties, like high-T_c superconductivity or colossal magnetoresistence (CMR). Recent and new anelastic spectroscopy experiments are presented, which supply information on the dynamics of such inhomogeneities in the superconductors of the La_2?xSr_xCuO₄ (LSCO) family and on the magnetic perovskite La_1?xCa_xMnO₃. In La_2?xSr_xCuO₄, a relaxation process at liquid He temperatures is identified as due to the motion of the hole stripes, acting as walls between antiferromagnetic (AF) domains. Another process is identified as the depinning of these stripes from defects in the disordered phase. In La_1?xCa_xMnO₃ a glassy dynamic response below the ferromagnetic (FM) transition is attributed to the insulating nanodomains coexisting with the ferromagnetic background.