SUPERCONDUCTIVITY AND MAGNETISM OF BI2SR2CACU2OX - EFFECT OF QUENCHING AND PULVERIZATION

The effect of quenching on Bi2Sr2CaCu2O(x) (BSCCO) has been investigated. Quenching enhances the critical temperature T(c). The hole concentration n(h) (approximately 5 x 10(21) cm-3) decreases as the quenching temperature T(q) increases. The normal-state static susceptibility chi-DC (approximately 5 x 10(-7) emu/g) of the BSCCO pellet is almost independent of temperature but its magnitude decreases with the increase of T(q). Thermogravimetry (TG) analysis shows that the change in the oxygen content is very small when the sample is heated. The Cu nuclear quadrupole resonance (NQR) spectra are very broad. In addition, we have observed a large Curie-Weiss term in chi-DC and chi-ESR of powdered samples. From the Curie constant, the number of localized Cu2+ spins is estimated to reach 30% of total Cu atoms. This component almost disappears by re-annealing. In all cases, chi-ESR has almost the same magnitude as chi-DC, in marked contrast with YBa2Cu3O7-delta. The origin of the normal-state susceptibility is discussed.