Abstract
We show that -NMR spectra place strong constraints on both the nature and the concentration of oxygen defects in ortho-II . Systematic deviation from ideal ortho-II order is revealed by the presence of inequivalent Cu sites in either full or empty chains. The results can be explained by two kinds of defects: oxygen clustering into additional chains, or fragments thereof, most likely present at all concentrations , and oxygen vacancies randomly distributed in the full chains for only. Furthermore, the remarkable reproducibility of the spectra in different samples with optimal ortho-II order shows that chain-oxygen disorder, known to limit electronic coherence, is ineluctable because it is inherent to these compounds.
- Received 23 June 2014
- Revised 30 March 2016
DOI:https://doi.org/10.1103/PhysRevB.93.134518
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