MAGNETISM AND SUPERCONDUCTIVITY IN THE 2/2/1/2 BISMUTH CUPRATE BY DYSPROSIUM SUBSTITUTION (BI2SR2CA1-XDYXCU2O8+DELTA)

Magnetic and superconducting properties of the solid solution Bi2Sr2[Ca1-xDyx]1Cu2O8+delta are reported. It is shown that substitution of Dy3+ for Ca2+ as well as appropriate annealings at moderate temperatures (300-degrees-C less-than-or-equal-to T less-than-or-equal-to 500-degrees-C), are efficient methods to optimize the critical temperature of the 2:2:1:2 bismuth cuprate. Emphasis is given to the interplay between magnetism and superconductivity in these materials. Results show that the dysprosium substitution is responsible for the magnetic properties in both the normal and superconducting states but, at the same time, it provides additional electrons which change the hole carrier density. As a consequence, paramagnetic domains would grow at the expense of the superconducting regions and will suppress superconductivity at x approximately 0.5.