Ni-induced local distortions in La{sub 1.85}Sr{sub 0.15}Cu{sub 1-y}Ni{sub y}O{sub 4} and their relevance to T{sub c} suppression: An angular-resolved XAFS study
We present results from angular-resolved x-ray-absorption fine-structure (XAFS) measurements at the Ni, La, and Sr K edges of oriented powders of La{sub 1.85}Sr{sub 0.15}Cu{sub 1-y}Ni{sub y}O{sub 4}, with y=0.01, 0.03, 0.06. A special magnetic alignment procedure allowed us to measure pure c- and ab-oriented XAFS at the Ni K edge in identical fluorescence geometries. Both the x-ray-absorption near-edge structure and the XAFS unequivocally show that the NiO{sub 6} octahedra are contracted along the c axis by {approx}0.32{angstrom} relative to CuO{sub 6} octahedra while the in-plane distances of NiO{sub 6} and CuO{sub 6} octahedra are the same within 0.01{angstrom}. The NiO{sub 6} octahedral contraction drives the average c axis contraction measured by diffraction with increasing content of Ni. The local c axis shows strong spatial fluctuations, due to the different NiO{sub 6} and CuO{sub 6} octahedral configurations and the stronger bonding of a La{sup 3+} ion than a Sr{sup 2+} ion to the O(2) apical oxygens of such octahedra. We discuss the relevance of these findings to the mechanisms of loss of superconductivity at y{approx}0.03 and hole localization above y{approx}0.05 by Ni dopants.
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FG03-98ER45681; W-31-109-Eng-38
- OSTI ID:
- 40277529
- Journal Information:
- Physical Review B, Vol. 64, Issue 10; Other Information: DOI: 10.1103/PhysRevB.64.104510; Othernumber: PRBMDO000064000010104510000001; 029134PRB; PBD: 1 Sep 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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