Structure and magnetic interaction in organic radical crystals. 6. Spin-transfer crystals: A theoretical study

The nature of the spin exchange interaction in half-filled bands of one-dimensional (1-D) stacks of mixed molecular radical crystals (MMRC) with the general formula ...R- .....H....R-.....H.... (R-. is a pi radical, and H is a diamagnetic polycyclic molecule) has been investigated theoretically. The intermolecular interaction is accompanied by spin transfer from R-. to H and determines the spin-spin interaction within the 1-D stacks of the MMRCs. The nature and the magnitude of the magnetic interaction in these structures are investigated using the band theory. At a given topology and geometry of the MMRC stacks the antiferromagnetic interaction in the parent molecular radical crystals ...R-.....R-..... becomes ferromagnetic in the MMRCs and vice versa. It was found that the effective exchange integral J(eff) of MMRCs, belonging to a given group with one and the same radical but different H, is proportional to the diamagnetic susceptibility chi(H). A new topological effect of the exchange interaction in MMRCs is formulated