STRUCTURE AND SUPERCONDUCTIVITY OF RARE-EARTH-DOPED LA2-XSRXCUO4

We present results of a detailed investigation of the structural phase transitions and their influence on superconductivity in rare earth do ped La2-xSrxCuO4. The structural transitions are predominantly determi ned by size differences of the atoms in alternating layers of the stru cture. In contrast to the findings in Ba-doped La2CuO4 the influence o f the low temperature transition on the electronic properties is not r estricted to a narrow hole doping around x similar or equal to 1/8. Ou r data show a strong influence of the buckling of the planar (Cu-O-Cu) bonds on the electronic properties. In particular, superconductivity disappears in the low temperature tetragonal phase if the buckling exc eeds a critical strength.