Competition of the antiferromagnetic superexchange with the ferromagnetic double exchange in dicobalt complexes

Abstract

Here we report the competition of superexchange and double exchange interactions in the molecule [(NH3)4Co(OH)2Co(NH3)4]4+. Magnetic data reveal a S=3 ground state arising from the competition. The canting angle between the magnetic moments of the Co2+ and Co4+ ions is about 92.5°. The double exchange parameter is estimated to be sevenfold of the superexchange parameter. The result presented here opens a way to introducing of ferromagnetic double exchange interaction to the single molecular magnets via the charge disproportionation between valence-variable transition-metal ions.