Scattering Studies of the High T$_c$ Superconductor La$_{2-x}$Ba$_{x}$CuO$_{4}$

The interplay between superconductivity, magnetism and crystal structure is a central issue in the study of the high T$_c$ cuprates. The first to be discovered, the Bednorz-M\"{u}ller materials have been much less extensively studied due to the difficulty of growing large single crystals. Using floating zone image furnace techniques, we have recently successfully grown La$_{2-x}$Ba$_{x}$CuO$_{4}$ (x$\sim$0.095 and 0.08) single crystals on the underdoped side of the well known 1/8 anomaly. X-ray studies show a sequence of crystal structures with temperature, while incommensurate elastic peaks associated with the low temperature tetragonal phase are observed using neutron diffraction. This signature of static spin stripe order persists into the superconducting state. We discuss the relationship between the low temperature spin and lattice degrees of freedom, as well as their sensitivity to doping level.