Intra-atomic exchange and ferromagnetic interaction in metallocene-based donor-acceptor stacked crystals
Phys. Rev. B 46, 5357 – Published 1 September, 1992
DOI: https://doi.org/10.1103/PhysRevB.46.5357
Abstract
A model explaining the nature of ferromagnetic exchange in organometallic charge-transfer molecular stacks is presented. It arises because of both the weak delocalization of unpaired electrons occupying the acceptor sites and the ferromagnetic exchange interaction between slightly delocalized acceptor electrons and perfectly localized ones in the d orbitals of the donor sites. It is shown that both the ground state of the system and the low-energy excitations can be described (in line with Anderson’s theory of exchange in insulators) with use of a one-dimensional Heisenberg spin Hamiltonian with ferromagnetic nearest-neighbor interactions. Theoretical estimates of the effective exchange parameter of the Heisenberg Hamiltonian agree with those obtained from experimental data on magnetic susceptibility and specific heat.