Physical Properties of SuperconductivityNo Access

INVESTIGATIONS ON THE EPR g FACTORS FOR THE SIX-COORDIANTED Cu²⁺(1) SITE IN YBa₂Cu₃O_6+x

Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China

International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, P. R. China

Corresponding author. Corresponding address: Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China.

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J. S. YAO

Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China

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H. M. ZHANG

Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China

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G. D. LU

Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China

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https://doi.org/10.1142/S0217979207044305Cited by:10 (Source: Crossref)

Abstract

The EPR g factors g_// and g_⊥ for the six-coordinated Cu²⁺(1) site in YBa₂Cu₃O_6+x are theoretically investigated from the perturbation formulas for a 3d⁹ ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu²⁺(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu²⁺ cluster. Based on the calculations, the effective elongation (≈ 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Δg (=g_// - g_⊥). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.

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