Low temperature phase transition and superconductivity in ( Nd)SrCuO

Abstract In ( La RE)SrCuO with RE = Nd, Eu, Gd, Dy, Tb we find besides the known tetragonal → orthorhombic transition a further low temperature structural phase transition to a tetragonal phase (probably P4 2 /ncm). A detailed phase diagram of La 1.85−x Nd x Sr 0.15 CuO 4 including structural and superconducting properties is presented. There is a competition between superconductivity and this low temperature phase transition: We observe no bulk superconductivity in the low temperature phase and no structural phase transition in the superconducting state.