Electron Paramagnetic Resonance Spectroscopy of Inorganic Materials

Terminological confusions and problems at the interface between the crystal field Hamiltonians and the zero-field splitting Hamiltonians—Survey of the CF=ZFS confusion in recent literature

“…As discussed [48,51], the orthorhombic standardization is embedded in the two conventions for the range of λ ¼E/D adopted in the EMR area [67,68] which are inherently related with selection of the principal axes of the ZFS 'tensor' D. The first standard convention: 0 r λ r 1/3 is mostly used in EMR studies of transition-metal ions [69,70]. In terms of the diagonal components of the conventional ZFS D tensor (S Á D Á S) this convention corresponds [67,68,71,72] to |D XX | r |D YY | r |D ZZ |, whereas the second one À 1/3 r λ r 0 corresponds to |D YY | o |D XX | r |D ZZ | [69,73,74].…”

“…In terms of the diagonal components of the conventional ZFS D tensor (S Á D Á S) this convention corresponds [67,68,71,72] to |D XX | r |D YY | r |D ZZ |, whereas the second one À 1/3 r λ r 0 corresponds to |D YY | o |D XX | r |D ZZ | [69,73,74]. Each convention is equivalent to the choice of the direction of the maximum overall splitting of an EPR spectrum as the Z axis, whereas that of the minimum as the X axis and Y axis in the former and latter convention, respectively [75,76].…”

“…In many papers the prevailing convention: 0 r λ ¼E/ D r 1/3 is taken for granted, as it is the case also, e.g. in the recent review [69], quote: 'Conventionally, |D zz | 4 |D yy | 4 |D xx |, and in such a case, E/D is always positive, varying between 0 and 1/3.' However, it is worth to keep in mind that all such conventions are, in fact, closely related to the standardization idea and represent its important implication.…”