Phenomenological Description of Aggregates of Exchange‐Bonded Paramagnetic Ions in Crystalline Environment. I. Effective Hamiltonian Formalism

Abstract

AbstractA general effective Hamiltonian formalism is proposed and applied to the phenomenological description of energetic structure of aggregates consisting of several exchange‐bonded paramagnetic ions in a crystalline environment. The low‐lying energetic multiplets of such a system, resulting from isotropic exchange (superexchange) interaction, split under the further interactions and, for a variety of ions, can be described in terms of effective spin Hamiltonians. Such a description is highly useful from the electron paramagnetic resonance point of view, in which the transitions inside multiplets are observed. The microscopic model for the phenomenologic constants of these Hamiltonians is given in the second order of perturbation treatment, and the case of ions with orbitally nondegenerate ground crystal term is discussed in some detail.