Trends in orthorhombic crystal field parameters for trivalent rare-earth ions in high-Tc superconductors REBa2Cu3O7−δ – Correct interpretation based on standardization

Trends in orthorhombic crystal field parameters (CFPs) reported for RE3+ ions in high-Tc superconductors REBa2Cu3O7−δ are considered. The cases of trends based on the CFP sets belonging to different regions of CF parameter space are identified and clarified. The crucial feature of such correlated alternative CFP sets is their intrinsic incompatibility. This makes meaningless direct comparisons of such CFP sets and thus presentations of CFP trends involving a mixture of alternative CFP sets. The aim of this paper is to ascertain that correct interpretation of trends in orthorhombic CFPs must be based on standardization. Examples of graphs inappropriately representing trends in orthorhombic CFPs reported for REBa2Cu3O7−δ compounds are considered and the corrected graphs based on the standardized CFP sets are provided.

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► Trends in orthorhombic crystal field parameters for RE3+ in REBa2Cu3O7−δ studied.
► Aspects related to crystal field parameter (CFP) standardization considered.
► Inappropriate representations of CFP trends identified and discussed.
► Correct interpretation of CFP trends must be based on standardization.