Magnetic coordination polymers can exhibit controllable magnetism by introducing responsiveness to external stimuli. This report describes the precise control of magnetism of a cyanide-bridged bimetallic coordination polymer (Prussian blue analogue: PBA) through use of an electrochemical quantitative Li ion titration technique, i.e., the galvanostatic intermittent titration technique (GITT). K 0.2Ni[Fe(CN) 6] 0.74.7H 2O (NiFe-PBA) shows Li ion insertion/extraction reversibly accompanied with reversible Fe 3+/Fe 2+ reduction/oxidation. When Li ion is inserted quantitatively into NiFe-PBA, the ferromagnetic transition temperature T C gradually decreases due to reduction of paramagnetic Fe 3+ to diamagnetic Fe 2+, and the ferromagnetic transition is completely suppressed for Li 0.6(NiFe- PBA). On the other hand, T C increases continuously as Li ion is extracted due to oxidation of diamagnetic Fe 2+ to paramagnetic Fe 3+, and the ferromagnetic transition is nearly recovered for Li 0(NiFe-PBA). Furthermore, the plots of T C as a function of the amount of inserted/extracted Li ion x are well consistent with the theoretical values calculated by the molecular-field approximation.
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