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 Bi 2 Sr 2 Y 1− x Ca x Cu 2 O y 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 Bi 2 Sr 2 Y 1− x Ca x Cu 2 O y with Ca content x ranging from 0.0 to about 0.3. The Néel temperature T N decreases with increasing Ca content; T N 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 Bi 2 Sr 2 Y 1− x Ca x Cu 2 O y system is thus similar to that of YBa 2 Cu 3 O x or La 2− x A x CuO 4−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 Bi 2 Sr 2 YCu 2 O y is also discussed.