INTERNAL MAGNETIC-FIELDS AT MU+ SITES AND THE MAGNETIC PHASE-DIAGRAM OF BI2SR2Y1-XCAXCU2OY SYSTEM STUDIED BY THE MU-SR METHOD

The magnetic properties of the Bi2Sr2Y1-xCaxCu2Oy system have been studied by positive muon spin rotation or relaxation methods. The magnetic phase diagram has been obtained as a function of Ca content x and temperature T. A long-range magnetic ordering (probably antiferromagnetic) has been observed in Bi2Sr2Y1-xCaxCu2Oy with Ca content x ranging from 0.0 to about 0.3. The Néel temperature TN decreases with increasing Ca content; TN is above 300 K for x=0.0, 200-250 K for x=0.2 and drops abruptly to 10-20 K for x=0.3. Superconductivity sets in around the same Ca content (x≈0.5) where the magnetic ordering disappears completely. The magnetic phase diagram of the Bi2Sr2Y1-xCaxCu2Oy system is thus similar to that of YBa2Cu3Ox or La2-xAxCuO4-δ (A=Sr or Ba) and suggests a common origin of the superconductivity in all these oxide superconductors. The temperature dependence of the internal magnetic field at μ+ in Bi2Sr2YCu2Oy is also discussed. © 1990.