On the non-standard rhombic spin Hamiltonian parameters derived from Mössbauer spectroscopy and magnetism-related measurements

Can the low symmetry crystal (ligand) field parameters be considered compatible and reliable?

“…The computer package CST [28,29] facilitates (unit and notation) conversions [21,22], standardization [16,17], and transformations [21], thus providing useful tools for comparison of apparently different but physically equivalent non-standard ZFSP [30][31][32] and CFP [33] data sets expressed in various notations and axis systems. The survey and reanalysis of the experimental non-standard data sets [30][31][32][33] removes their incompatibility and indicates that many authors are still unaware of the standardization idea [16,17] and its usefulness. The recent reviews on the spin Hamiltonian formalisms [34] and the (often confused) interrelations between the CF and ZFS quantities [35] as well as the note on the incorrect orthorhombic ZFSPs relations [36] may also be useful to consult.…”

“…Meaningful comparison of such correlated CFP data sets may be achieved due to the orthorhombic standardization [16,17,28,29] discussed in Section 2. The usefulness of standardization has been amply illustrated for CFP data sets [16,28,33] and ZFSP ones [16,[30][31][32].…”

“…Due to the standardization transformations the non-standard fitted CFP data sets, obtained by various authors often using different experimental techniques, expressed originally in various nominal axis systems (as defined in Section 3), can be transformed into a 'common' nominal axis system. Researchers [50][51][52][53][54][55][56] who did applied standardization transformation, including CZR [16,17,[30][31][32][33]57], have seemingly not realized that all such transformations have only relative nominal and not definite meaning if applied to the fitted CFP data sets. Only for the theoretical CFP data sets, given in the axis systems well defined w.r.t.…”

Electron paramagnetic resonance study of Fe3+ ions at octahedral and tetrahedral mirror symmetry sites in the LiScGeO4 crystal

“…The ZFS and the spectrum anisotropy are mainly determined by the relatively large values of the rank-2 ZFS parameters for both centers, which are of the same order of magnitude as for Fe 3 § ions at the mirror symmetry sites in forsterite [2] and chrysoberyl [4]. In the principal axis system of the rank-2 ZFS tensor chosen to satisfy the orthorhombic standardization [15,16] (2) M=I Oxygen-coordinated Fe 3 § ions at the octahedral sites exhibit distinctly larger values of S 4 [17]. The value of S 4 for Fe3+(I) in Table 1 is about three times larger than that for Fe3+(II) and implies the validity of the assignment of Fe3+(I) and Fe3+(II) in LiScGeO4:Cr to the octahedral and tetrahedral sites, respectively.…”

Reanalysis of crystal field parameter datasets for rare-earth ions at low symmetry sites: Nd3+ in NdGaO3 and Pr3+ in PrGaO3

“…The problems discussed above reduce even further the reliability of the CFP dataset [1]. Nevertheless, to satisfy the general criteria [30][31][32][33] for a meaningful comparison of low symmetry CFP datasets we bring the datasets [1,2] to a comparable form presented in Table 1.…”