Theoretical studies of d– d and d–π– d magnetic interactions in (EDT-TTFVO) 2FeBr 4 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) 2FeBr 4 crystal based on the X-ray crystallographic structures at 113 K. 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 0.4 K. 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.