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617974 
Journal Article 
Low symmetry aspects inherent in electron magnetic resonance (EMR) data for transition ions at triclinic and monoclinic symmetry sites: EMR of Fe3+ and Gd3+ in monoclinic zirconia revisited 
Rudowicz Ca; Gnutek, P 
2008 
403 
13-16 
2349-2366 
Abstract: Our recent survey of the EMR literature has revealed a number of experimental zero-field splitting (ZFS) parameter datasets for transition ions at triclinic symmetry sites in various compounds, which include for a given rank (k=2, 4, 6) all components −k⩽q⩽+k. Model calculations of ZFS parameters, which usually employ the crystallographic axis system centered at the transition ion, may also yield triclinic-like ZFS parameter datasets. Closer analysis is required in order to distinguish the actual low symmetry aspects from the apparent ones. A comprehensive approach is proposed to analyze the low symmetry aspects involved in the monoclinic- or triclinic-like spin Hamiltonian (SH) terms, especially the ZFS ones. The approach comprises three methods: (i) finding the principal values of the various 2nd-rank SH terms and the orientation of the respective principal axis systems w.r.t. the laboratory or crystallographic axis system, (ii) extending the cubic/axial pseudosymmetry axes method (PAM) to lower symmetry cases and finding the pseudosymmetry axis system for the 4th-rank ZFS parameters, and (iii) employing the closeness factors C and the norms ratios R=N A/N B for quantitative comparison of several ZFS parameter datasets. Each method is facilitated by recently developed computer programs. Application of this approach, with focus on the PAM, for the ZFS parameter datasets for Fe3+ and Gd3+ in monoclinic zirconia (m-ZrO2) is presented. Our considerations enable better understanding of the low symmetry aspects as well as correlation of the principal axis systems and/or pseudosymmetry axis systems with the symmetry-adapted axis systems, which may be approximately related to the respective metal ion–ligands bonds. The equivalence between various physically equivalent ZFS parameter datasets generated by the first and second method, especially those transformed to the standard ... [Copyright 2008 Elsevier] Copyright of Physica B is the property of Elsevier Science Publishers B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts) 
SYMMETRY; ZIRCONIUM oxide; CRYSTALLOGRAPHY; ASTERISM (Crystallography)