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

Abstract

The orthorhombic standardization of spin Hamiltonian parameters is increasingly adopted in the electron magnetic resonance area. The aim of this paper is to elucidate the ramifications of orthorhombic standardization for other spectroscopic and magnetic techniques, which also employ the spin Hamiltonian formalism. This is illustrated by examples derived from the Mössbauer spectroscopy, magnetic moments and magnetic susceptibility, photoinduced changes of magnetization, and other magnetism-related measurements. Implications 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 scattering are also discussed. Several sets of the non-standard zero-field splitting (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 extended Stevens notation b k q and units of cm −1 together with the conventional D and E parameters, which prevail in the studies dealt with in this paper. This enables a direct comparison with the available data for similar ion/host systems. The standardization reveals several inconsistencies in interpretation of the experimental data obtained by various techniques.