Oxygen ordering in the high-T-c superconductor HgBa2CaCu2O6+delta as revealed by perturbed angular correlation

resumo

Lattice sites and collective ordering of oxygen atoms in HgBa2CaCu2O6+delta were studied using the perturbed angular correlation (PAC) technique at ISOLDE/CERN. The electric field gradients (EFG) at Hg-199m nuclei have been measured as functions of oxygen doping on the Hg planes, above and below T-c. In comparison with the results obtained for oxygen and fluorine doping in Hg-1201, the analysis shows a different oxygen ordering exhibited by Hg-1212. Moreover, for all studied cases, the experimental results show that at a local scale there is non uniform oxygen distribution. A series of ab initio EFG calculations allowed to infer that at low concentrations, regions without oxygen coexist with regions where O-2 delta dumbbell molecules are located at the center of the Hg mesh. On the other side, at high concentrations, O-2 delta dumbbell molecules coexist with single O-delta atoms occupying the center of the Hg mesh. The present results suggest that oxygen sits on the Hg planes in the form of a molecule and not as a single atom.

palavras-chave

NEUTRON POWDER DIFFRACTION; STRUCTURAL-CHANGES; CRYSTAL-STRUCTURE; HGBA2CUO4+DELTA; BI2SR2CACU2O8+DELTA; DEPENDENCE; HGBA2CA2CU3O8+DELTA; INTERSTITIALS; PRESSURE; BEHAVIOR

categoria

Physics

autores

Mendonca, TM; Correia, JG; Haas, H; Odier, P; Tavares, PB; da Silva, MR; Lopes, AML; Pereira, AM; Goncalves, JN; Amaral, JS; Darie, C; Araujo, JP

nossos autores

agradecimentos

This work was supported by the Portuguese Foundation for Science and Technology, FCT, with the project CERN-FP-109272-2009, by the German BMBF funding resources, and by the ISOLDE collaboration with approved project IS360. T. M. M. acknowledges FCT Ph.D. Grant No. SFRH/BD/29445/2006. The authors gratefully thank V. S. Amaral, P. Bordet, and T. Hansen for fruitful discussions, and M. B. Barbosa, R. P. Vilhena, and M. Bacia for support during experiments.

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