Ni-induced local distortions in La1.85⁢Sr0.15⁢Cu1−��⁢Ni��⁢O4 and their relevance to ���� suppression: An angular-resolved XAFS study

Abstract

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 La1.85⁢Sr0.15⁢Cu1−��⁢Ni��⁢O4, with �� =0.01, 0.03, 0.06. A special magnetic alignment procedure allowed us to measure pure ĉ- 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 NiO6 octahedra are contracted along the c axis by ≈0.32⁢Å relative to CuO6 octahedra while the in-plane distances of NiO6 and CuO6 octahedra are the same within 0.01⁢Å. The NiO6 octahedral contraction drives the average ĉ axis contraction measured by diffraction with increasing content of Ni. The local ĉ axis shows strong spatial fluctuations, due to the different NiO6 and CuO6 octahedral configurations and the stronger bonding of a La3+ ion than a Sr2+ 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 ��≈0.03 and hole localization above ��≈0.05 by Ni dopants.

Department(s)

Materials Science and Engineering

Comments

DOE Contract number FG03-98ER45681; W-31109-ENG-38

International Standard Serial Number (ISSN)

2469-9969, 2469-9950

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 American Physical Society, All rights reserved

Publication Date

2001-08-21

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