CRYSTAL-STRUCTURE AND SUPERCONDUCTIVITY OF (LA,SR)2CUO4/SM2CUO4 SUPERLATTICES PREPARED BY EXCIMER LASER DEPOSITION

We have grown superlattices of (La,Sr)2CuO4/Sm2CuO4 [1/1 to 120/120] onto SrTiO3 substrates by an excimer laser deposition technique. These superlattices can be classified into three regions. For the short periodicity of the stacking up to 4/4, new structures are constructed having a large unit cell made of a CuO5 pyramid, CuO6 octahedral, and CuO4 sheet. For the large periodicity more than 60/60, the superlattices exhibit the same superconducting behavior as the standard (La,Sr)2CuO4. The superlattices of the intermediate periodicity, from 60/60 to 15/15 on the other hand, show changes in the critical temperature as the variation of the stacking periodicity. This phenomenon is explained to be derived from a pressure effect caused by a lattice mismatch between (La,Sr)2CuO4 and Sm2CuO4 layers.