Magnetic studies of strontium lanthanum copper oxides.

We report measurements of static magnetic susceptibilities for a series of strontium substituted lanthanum copper oxides prepared under identical conditions. These materials have recently been shown to exhibit bulk superconductivity with high critical temperatures. Measurements of the end member La sub 2 CuO sub 4 provide evidence for a phase transition of unknown origin at 260K. This phase transition is suppressed by the substitution of small amounts of strontium for lanthanum. Understanding the normal state properties of Sr sub x La sub (2-x) CuO sub (4-delta) may provide important clues to the superconducting behavior of these materials.