Z. Naturforsch. 68a, 442 – 446
Theoretical Investigations of the Knight Shifts and the Hyperfine Structure Constants for the Tetragonal Cu2+ Sites in the Bismuth- and Thallium-Based High-Tc Superconductors
1 School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
2 International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, P. R. China
Received December 3, 2012 / revised February 4, 2013 / published online May 1, 2013
The Knight shifts and hyperfine structure constants for the tetragonal Cu2+ sites in bismuth- and thallium-based high-Tc superconductors (Bi1.6Pb0.4Sr2Ca2Cu3O10, TlSr2CaCu2O7–y, and Tl2Ba2CuOy) are theoretically investigated from the high-order perturbation formulas of these parameters for a 3d9 ion under tetragonally elongated octahedra in a unified way. The calculation results show good agreement with the observed values. The significant anisotropies of the Knight shifts are attributed to the local tetragonal elongation distortions of the five-(or six-)coordinated Cu2+ sites in these systems. The present studies would be beneficial to establish a complete
physical scheme for unified understandings of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectral behaviours of Cu2+ (or other similar 3d9 ions) in the high-Tc superconductors.
Key words: Knight Shifts; Hyperfine Structure Constants; 63Cu2+; Bi1.6Pb0.4Sr2Ca2Cu3O10; TlSr2CaCu2O7–y; Tl2Ba2CuOy.