A ROOM-TEMPERATURE ORGANOMETALLIC MAGNET BASED ON PRUSSIAN BLUE

THE rational design of molecular compounds that exhibit spontaneous ma gnetic ordering might enable one to tailor magnetic properties ties fo r specific applications in magnetic memory devices(1-4). In such mater ials synthesized previously(5-17), however, the underlying weak magnet ic interactions are incapable of maintaining ordering at ambient tempe ratures. One remarkable exception is a compound derived from vanadium and tetracyanoethylene(18), but the material is amorphous and fragile, and consequently the molecular interactions responsible for its strik ing properties are not understood. Here we demonstrate another route t o the synthesis of a room-temperature organometallic magnet, in which we combine a hexacyanometalate [M(CN)6](q-) with a Lewis acid L(p+). I f L and M are transition-metal ions, then the orbital interactions in the resulting compound can be described by well understood principles( 21-24), and it is therefore possible to choose the metals to tune the compound's magnetic properties-in particular, the magnetic ordering (C urie) temperature T-c(refs 21-26). We have synthesized a room-temperat ure magnetic material (T-c=315 K) that belongs to the Prussian blue fa mily of compounds(27) (where M is chromium and L is vanadium), demonst rating that transition-metal hexacyano complexes are promising compone nts for the construction of molecule-based high-T-c magnets.