Universal superconducting and magnetic properties of the (CaxLa1−x)(Ba1.75−xLa0.25+x)Cu3Oy system: a μSR investigation

The (CaxLa1−x)(Ba1.75−xLa0.25+x) Cu3Oy system is ideal for testing theories of high temperature superconductivity, since nearly the full range of doping is controlled by y, and Tcmax is continuously controlled by x, with minimal structural changes. We investigate this system with both transverse and longitudinal field μSR. This allows us to re-examine the Uemura relation, the nature of the spontaneous magnetic fields below Tc, and the relation between their appearance temperature Tg and Tcmax. Our major findings are: (1) the Uemura relation is respected by this system more adequately than by other cuprates, (2) Tg and Tc are controlled by the same energy scale, (3) the phase separation between hole poor and hole rich regions is a microscopic one, and (4) spontaneous magnetic fields appear gradually with no moment size evolution.