Dependence of physical properties on Bi/Sr ration and oxygen content of Bi<sub>2+x</sub>Sr<sub>2-x</sub>CaCu<sub>2</sub>O<sub>8+δ</sub>
POSTER
Abstract
In order to extract the fundamental physical properties of high transition temperature (high-Tc) superconductors, one needs to take account of the details of real materials which possibly affect their properties. In the case of Bi2Sr2CaCu2O8+δ (Bi2212), non-stoichiometry due to the intersubstitution between Bi and Sr atoms exists, yielding its composition Bi2+xSr2-xCaCu2O8+δ. Accordingly, the number of hole carries (nh) as well the magnitude of chemical inhomogeneity depends on x and δ (oxygen content). In order to evaluate the precise x- and δ- dependence of the physical properties, high-quality single crystals of Bi2212 with x=0.10, 0.15, and 0.20 were grown by the Travelling-Solvent Floating Zone (TSFZ) method. The δ values were systematically changed by annealing the as-grown crystals under various conditions. To evaluate nh, we performed XAFS measurements, in which the pre-peak intensity of the oxygen K-edge absorption spectra is known to a measure of nh. We have successfully established the relationship between nh and Tc of the Bi2212 system with different amount of chemical inhomogeneity (x’s). The details of these characteristics will be presented in the meeting.
Presenters
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Syungo Nakagawa
- Univ of Tsukuba
- University of Tsukuba