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

The (Ca x La 1-x )(Ba 1.75-x La 0.25+x )Cu 3 O y system is ideal for testing theories of high temperature superconductivity, since nearly the full range of doping is controlled by y, and T max c 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 T c , and the relation between their appearance temperature T g and T max c . Our major findings are: ( I ) the Uemura relation is respected by this system more adequately than by other cuprates, (2) T g and T c 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.