Structural and superconducting properties of Bi2Sr2Ca(Cu1−yCoy)2O8+δ single crystals
1992; Elsevier BV; Volume: 198; Issue: 1-2 Linguagem: Inglês
10.1016/0921-4534(92)90262-b
ISSN1873-2143
AutoresM. Boekholt, Th. Bollmeier, L. Buschmann, M. Fleuster, G. Güntherodt,
Tópico(s)Advanced Condensed Matter Physics
ResumoIn Bi2Sr2Ca(Cu1-yCoy)2O8+δ single crystals, the Cu-ions have been substituted by Co up to the limit of existence of the Bi-2212 phase, which is at y=0.08. With increasing y, there results an increasing, strong deficiency of earth alkali-atoms compared to the stoichiometric composition. This increasing disorder with increasing y yields a decrease of the lattice constant and a broadening of the Raman-active phonons. The transition temperatures decrease linearly with increasing y with a slope of about 5 K/{Co/(Cu+Co)} at.%, i.e. for every percent Cu substituted by Co Tc is reduced by 5 K. At the maximum value of y=0.08 we obtain Tc=45 K. The energy of the superconducting gap decreases with increasing y, but stronger than expected by the linear relation 2Δ‖(0)/kBTc=5.7±0.2 observed for oxygen-deficient, pure Bi2Sr2CaCu2O8+δ (y=0) single crystals.
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