Theoretical studies of d–d and d–π–d magnetic interactions in (EDT-TTFVO)2FeBr4 crystals

Abstract: The effective exchange integrals (J(HB)) of the Heisenberg spin model have been evaluated by using the ab initio MO and based on Hartree–Fock (HF) and density functional theory (DFT) for organic magnetic metals, the (EDT-TTFVO)2FeBr4 crystal based on the X-ray crystallographic structures at 113K. In order to study the magnetic properties, we proposed some of the pairs, where the direct (d–d) and indirect (d–π–d) magnetic couplings between Fe(III) d-spins (S =5/2) without/with π-dimer spins (S =1/2) were calculated, respectively. The effective exchange integrals were evaluated by using UB3LYP method, and principal J values were 0.5, −0.1 and 0.4K. From these results, it is found that there were three dimensional spin arrangements of Fe(III) d-spins. The Quantum Monte Carlo (QMC) simulations had been carried out with our calculated J values to evaluate the magnetic susceptibility for this molecular crystal, reproducing the experimental tendency. [Copyright &y& Elsevier]