Characterization of a new Pb-based 1222 cuprate Pb(Sr<sub>1.2</sub>La<sub>0.8</sub>)Gd<sub>2</sub>Cu<sub>2</sub>O<sub>9.06</sub>
Jinrong Min; Jingkui Liang; Cong Wang; Fei Wu; Cheng Dong; Guanghui Rao; Jinrong Min; Inst. of Phys., Chinese Acad. of Sci., Beijing, China; Jingkui Liang; Inst. of Phys., Chinese Acad. of Sci., Beijing, China; Cong Wang; Inst. of Phys., Chinese Acad. of Sci., Beijing, China; Fei Wu; Inst. of Phys., Chinese Acad. of Sci., Beijing, China; Cheng Dong; Inst. of Phys., Chinese Acad. of Sci., Beijing, China; Guanghui Rao; Inst. of Phys., Chinese Acad. of Sci., Beijing, China
Журнал:
Journal of Physics: Condensed Matter
Дата:
1995-07-24
Аннотация:
A new compound Pb(Sr<sub>1.2</sub>La<sub>0.8</sub>)Gd<sub>2</sub>Cu<sub>2</sub>O<sub>9.06</sub> has been synthesized and characterized in this letter. The Pb ions in the rock-salt-type monolayer of this compound occur in the form of mixed valence states, i.e., Pb<sup>4+</sup> and Pb<sup>2+</sup>, and the average cationic valence is 3.14, close to that in (Pb<sub>0.5</sub>Cd<sub>0.5</sub>)Sr<sub>2</sub>YCu<sub>2</sub>O<sub>7</sub>. It seems to us that the single-Pb-layer Pb-based layered compounds are stable only when the average cationic valence in this layer is close to three. The crystal structure refinement results indicate that the PbO layer is highly distorted, and no Cu ions enter this monolayer. The high distortion of the PbO layer makes the Pb-1222 phase preferentially orientate more readily. This compound does not superconduct. The nonsuperconductivity is not caused by low charge carrier concentration. It may be caused by the Gd<sub>2</sub>O<sub>2</sub> layers, which affect not only the buckling degree of conducting CuO<sub>2</sub> planes but the coupling effect between adjacent CuO<sub>2</sub> planes as well.
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