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

The orthorhombic standardization of spin Hamiltonian parameters is increasi ngly adopted in the electron magnetic resonance area. The aim of this paper is to elucidate the ramifications of orthorhombic standardization for othe r spectroscopic and magnetic techniques, which also employ the spin Hamilto nian formalism. This is illustrated by examples derived from the Mossbauer spectroscopy, magnetic moments and magnetic susceptibility, photoinduced ch anges of magnetization, and other magnetism-related measurements. Implicati ons of standardization in the studies of magnetic ordering, Haldane gap for integer spin systems, the macroscopic quantum tunnelling of magnetization, specific heat measurements, the spin wave theory, and inelastic neutron sc attering are also discussed. Several sets of the non-standard zero-field sp litting (ZFS) parameters for transition ions at orthorhombic symmetry sites , expressed in various notations and units, are standardized. Calculations are performed using the computer package CST, which yields the standardized ZFS parameter sets. The results are presented in a unified way in the exte nded Stevens notation b(k)(q) and units of cm(-1) together with the convent ional D and E parameters, which prevail in the studies dealt with in this p aper. This enables a direct comparison with the available data for similar ion/host systems. The standardization reveals several inconsistencies in in terpretation of the experimental data obtained by various techniques. (C) 2 001 Elsevier Science B.V. All rights reserved.