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Updated: Jun 27, 2026
Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
Isotropic non-Heisenberg terms in the magnetic coupling of transition metal complexes
Roland Bastardis1, Nathalie Guihéry, Coen de Graaf
1Laboratoire de Chimie et de Physique Quantiques, IRSAMC/UMR5626, Universite Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex 4, France.
Abstract:
This paper analyzes the different contributions to the magnetic coupling in systems with more than one unpaired electron per center. While in S=12 spin systems the Heisenberg Hamiltonian involving only bilinear exchange interactions is reliable for the description of the magnetic states, biquadratic exchange interactions must be sometimes introduced for S=1 (or higher) spin systems to account for isotropic deviations to Heisenberg behavior. The analysis establishes that the excited atomic states, the so-called non-Hund states, are responsible for the main contribution to the deviations. The kinetic exchange contribution and the spin, hole, and particle polarizations increase the magnetic coupling but essentially maintain the Heisenberg pattern. The importance of the different contributions has been studied for a series of Ni(2) compounds with a polarizable double azido bridge. The coupling between two Fe(3+) ions in the molecular crystal Na(3)FeS(3), which is known experimentally to present large deviations to Heisenberg behavior, has also been investigated.
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