Clarification of the confusion concerning the crystal-field quantities vs. the zero-field splitting quantities in magnetism studies: Part I—Survey of literature dealing with specific compounds

Physically distinct notions: (i) crystal field (CF) or equivalently ligand field (LF), (ii) magnetic or magneto-crystalline anisotropy (MA) or equivalently single-ion anisotropy, and (iii) exchange interactions (EI) or spin–spin couplings, appear to be confused in magnetism studies with zero-field splitting (ZFS) or equivalently fine structure (FS). Confusion X=Y consists in incorrect referral to the quantity Y by the name X of another well-defined quantity. Survey of magnetism literature indicates numerous cases of confusion of the type: CF=ZFS, MA=ZFS, EI=ZFS. Since muddled terminology is unhealthy for any area of science, each type of confusion must be clarified. In this review, the CF=ZFS confusion in magnetism literature dealing with specific compounds is clarified. To elucidate this confusion, the CF/LF and ZFS/FS quantities are briefly overviewed. The cases of terminology mixing up: the pertinent Hamiltonians, respective parameters, and energy level splittings, are systematically analysed, classified, and clarified. The structural and/or physical consequences of the confusion as well as of the non-standard parameters are also considered. Implications of each type of confusion go beyond the simple semantic issues and concern misinterpretation of data from a wide range of experimental techniques. The incorrect terminology contributes also to misleading keyword classifications of papers in journals and scientific databases.