Anomalous properties and microstructural model of superconductivity in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$(Ba,Sr${)}_{\mathit{x}}$${\mathrm{CuO}}_4$

A specific microstructural model involving short- or long-range order of (Ba,Sr${)}_{\left[\mathrm{La}\right]}$ dopant substituents explains the composition ${\mathit{x}}_0$=0.125 most favorable for the formation of the low-temperature ${\mathrm{Ba}}_{\left[\mathrm{La}\right]}$ tetragonal phase. The microstructural model shows that the normal state of these alloys can be described as a two-component Fermi liquid in order to explain the acoustic, magnetic, and thermal anomalies centered on ${\mathit{x}}_0$ as well as the related drastic reduction in ${\mathit{T}}_{\mathit{c}}$ over a narrow range of x.