Competition Between Structural and Superconducting Transition in (LaNd)-Sr-Cu-O

Experimental evidence is presented for a competition between the superconducting and a structural transition in La1.85−xNdxSr0.15CuO4 as a function of the Nd content. At high Nd concentration (x ≥ 0.18) a discontinuous, first-order structural transition is found, which destroys superconductivity and has a drastic influence on the normal-state transport properties. At lower Nd concentration (x < 0.18) a sharp superconducting transition occurs, which seems to suppress the structural phase transition.