Reanalysis of crystal-field parameters forNd3+ions inNd2BaCu

Abstract

This paper elucidates some subtle properties of the orthorhombic and monoclinic symmetry crystal-field ͑CF͒ Hamiltonians ͑H CF ͒, which are not fully understood by some authors. These properties bear on interpretation of experimental data obtained in, e.g., optical spectroscopy, inelastic neutron scattering, and magnetic susceptibility measurements. Our reanalysis of CF parameters ͑CFPs͒ is based on application of the standardization idea as well as the idea of dataset closeness. The closeness of any two CFP sets may be represented by the closeness factor C and the norm ratio R = N A / N B for the respective H CF terms: k =2,4,6, and the global ones C gl . The specific aims of this paper are twofold. The first aim is to clarify the controversy arising when comparing the standard CF parameters with the nonstandard CFPs. This controversy, originating from the lack of awareness of the standardization applicable to the orthorhombic ͑as well as monoclinic and triclinic͒ CFP datasets, is evident, e.g., in the recent study of Nd 3+ ion in Nd 2 BaCuO 5 by R. S. Puche et al. ͓Phys. Rev. B 71, 024403 ͑2005͔͒. This leads to an unjustified criticism of the data of other authors. Consideration of standardization and dataset closeness also helps in identifying other inconsistencies concerning R. S. Puche et al.'s results. The second aim is to determine the alternative physically equivalent CFP datasets generated by the standardization transformation. These CFP datasets are utilized in the multiple correlated fitting technique ͑MCFT͒ to improve the reliability of the final fitted CFPs. Additonal refittings of the original energy level data are carried out starting from distinct regions in the parameter space. The independently fitted nonstandard CFPs obtained in this way are then transformed to the standard region and intercorrelated. Our considerations enable us to solve the controversy in question and improve the understanding of the intricacies inherent in the low-symmetry CFP datasets. A comparative analysis of the CFPs for various rare earth R 3+ ions in R 2 BaXO 5 ͑X = Cu, Zn, Ni, and Co͒, and related crystals will be carried out elsewhere.

Alternative zero-field splitting (ZFS) parameter sets and standardization for Mn2+ ions in various hosts exhibiting orthorhombic site symmetry

“…recognized and discussed [45]. The number of applications of the standardization idea [6][7][8][9][10] has been growing since its comprehensive extensions appeared [20,21]; see the recent papers [22][23][24] and references therein.…”

“…Since the mid-1980 the standardization idea have also spread out into optical spectroscopy area and the number of pertinent applications for the orthorhombic CF parameters is growing steadily (for references, see, e.g., the recent papers [22,23,24]). …”

Comprehensive analysis of crystal field parameter datasets for transition ions at low symmetry sites and extracting structural information—Application to Pr4+ in BaPrO3

“…The closeness factors C p and the norms ratios R p provide means for quantitative comparison of various sets of n quantities of the same nature, e.g. the CFPs or the energy levels, considered as n-dimensional (nD) 'vectors' [1,7]. The principal axis systems and pseudosymmetry axes may be compared with the axis systems commonly used in the CF area.…”

“…The triclinic-like CFPs were calculated using the exchange charge model (ECM) by Popova et al [2]. Our comprehensive approach comprises three recently developed methods: (i) the procedure for diagonalization of the second-rank CFPs [3], (ii) an extension of the cubic/axial pseudosymmetry axes method of Bacquet et al [4] to lower symmetry cases [5], and (iii) quantitative comparison of CFP datasets and other quantities based on the closeness factors C p and the norms ratios R p = N A /N B for the respective H CF terms: p = k = 2, 4, 6, and the global (p = gl) ones [1,7]. The method (i) provides the principal values of the second-rank CFPs and the orientation of their principal axis systems w.r.t.…”

Alternative crystal-field parameters for rare-earth ions obtained from various techniques: II. Reanalysis of spectroscopic data for Eu3+ and Er3+ ions in RE2BaXO5 (X=Co, Cu, Ni, Zn) high temperature superconductors and related systems

“…Similarly, our reanalysis [3] of theoretical and experimental CFP sets [4,5] has enabled clarification of unjustified claims or misinterpretations concerning the non-standard [4] and standard [5] CFP sets for Nd 3+ in Nd 2 BaCuO 5 . The discrepancies concerning the CFP sets [2,4,5] identified in [1,3] appear to be mainly due to lack of awareness of the intrinsic distinction between the non-standard and standard orthorhombic CFP sets (as defined in [6,7]), which is still often occurring in literature.…”