ELECTRON-DOPED INFINITE-LAYER SR1-XLNXCUO2 SUPERCONDUCTORS - SYNTHESIS, MAGNETISM, AND TRANSPORT

We report the results of SQUID magnetization, x-ray diffraction, and transport studies of polycrystalline specimens of the electron-doped infinite-layer compounds Sr1-xLnxCuO2 (Ln = lanthanide element, x = 0-0. 16). Samples are synthesized at high pressure (25 kbar), typically at temperatures in the range 950-1085-degrees-C. X-ray diffraction data indicate that the solid solution phase boundary occurs at x almost-equal-to 0.10, somewhat lower than previously supposed. Magnetic and superconducting properties are a sensitive function of synthesis conditions, with optimal superconucting behavior (-4pichi almost-equal-to 0.6-0.9) observed for a very narrow (approximately 10-degrees-C) synthesis window. Only a small variation of T(c) (T(c) almost-equal-to 43 K) with dopant ion size is observed; a smaller T(c) for Ln = Gd may imply an appreciable rare-earth ion-conduction electron exchange coupling, J almost-equal-to 11 meV.