Nature of the magnetic interaction of Wurster's radicals in the solid state

Abstract The nature of the spin exchange interaction within the half-filled band in one-dimensional stacks of Wurster's radicals in Wurster's red bromide has been investigated theoretically. The various contributions to the Heisenberg effective exchange integral: direct, kinetic, and indirect spin exchange are evaluated quantitatively. It has been shown that the direct (Coulomb) exchange which causes the ferromagnetic coupling is small. The negative value of the effective exchange integral between Wannier functions, localized within the elementary units, has been determined by the kinetic and indirect (antiferromagnetic) exchange interaction.