Current status of the proposals for unification of notations and guidelines for data presentation in the EMR Area: Blueprint for future actions

Abstract

Abstraet. The tremendous development of the electron magnetic resonance (EMR), i.e., electron paramagnetic resonance (EPR), electron spin resonance (ESR), and related spectroscopic techniques, and their applications in a number of fields is accompanied by a rather messy situation in the underlying theoretical framework. This is especially true concerning the EPR of transition ions in crystals, where an abundance of notations and lack of widely accepted clear definitions of the basic theoretical concepts characterize the current situation. Asa consequence, proliferation of a number of terminological misconceptions and incorrect relations for the zero-field splitting parameters has taken place. Major problems detrimental for the future of EMR as well as the efforts aimed at alleviating these problems are reviewed. Rationales for coordinated activities in three major directions are outlined. This includes unification of spin Hamiltonian notations, unification of EMR nomenclature, and making better use of the various categories of data generated during EMR studies. 10verview of the Current Situation in the EMR AreaThis paper is an abbreviated version of a presentation at the 31st Congress Ampere [1]. A perusal of the review [2] and the articles collected in ref. 3 as well as the contents of the proceedings of recent electron magnetic resonance (EMR)-related conferences, e.g., the Asia-Pacific Electron Paramagnetic Resonance (EPR) (ESR) Society's (APES) Symposia: APES'97 [4], APES'99 [5], and APES'01 [6], provide a compelling evidence of the tremendous development of the experimental EMR techniques since the first observation of the paramagnetic resonance spectrum by Zavoisky in 1944 (see, e.g., reŸ 7). The perspective provided by the resources, e.g., in refs. 3-7, shows the present depth and breadth of the applications of EMR spectroscopy. Various specialized monographs (for references, see ref.2) may be consulted for specific aspects of modern applications of EMR evidenced in, e.g., refs. 3-6.On the theoretical side, the concept of spin Hamiltonian (SH) has become the comerstone underlying all EMR subareas. Most sophisticated forms of SH

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

“…Detailed guidelines may be worked out along the lines proposed recently for the guidelines for presentation of the EMR data [84]. There is also a strong need for a comprehensive database of the CF/LF parameters, which could be developed as an extension of the proposed EMR database [84]. Successful implementation of the proposals put forward here requires coordination of the activities at the international level in cooperation with the all scientific communities involved in the CF/LF studies.…”

“…The present considerations provide a firm basis for the unified guidelines for presentation of the CFP data sets. Detailed guidelines may be worked out along the lines proposed recently for the guidelines for presentation of the EMR data [84]. There is also a strong need for a comprehensive database of the CF/LF parameters, which could be developed as an extension of the proposed EMR database [84].…”

Intrinsically incompatible crystal (ligand) field parameter sets for transition ions at orthorhombic and lower symmetry sites in crystals and their implications

“…Comprehensive standardization of orthorhombic and monoclinic ZFSPs, including the 4 th -and 6 th -rank ZFSPs, have also been proposed in [51] and [48], respectively, in par with standardization of CFPs. Practical applications of standardization to ZFSPs have been considered in [32,48,51,97,116,117,118], whereas guidelines for appropriate conventions and unification of notations used in EMR spectroscopy have been advocated in [119,120,121].…”

The generalization of the extended Stevens operators to higher ranks and spins, and a systematic review of the tables of the tensor operators and their matrix elements

“…The feasibility of a large-scale verification of the existing EMR-related computer programs hinges upon concerted efforts and international collaboration of developers of various computer programs. The framework for such collaboration has been proposed by Rudowicz (2003aRudowicz ( , 2003b. At the present stage we can offer some specific comments regarding two programs.…”