Thermal-induced structural distortion, charge transfer and magnetic changes of Prussian blue analogs K0.4Co1.3[Fe(CN)6]•nH2O

The K0.4Co1.3[Fe(CN)6]center dot nH2O samples were prepared by co-precipitation method. Powder X-ray diffraction showed that only one HT phase existed in the sample prepared at room temperature ([KCoFe]RT). When the preparation temperature rises to 80 degrees C([KCoFe]80 degrees C), the diffraction peak intensity of primary HT phase weakened and another LT phase appeared. The HT and LT phase are both FCC crystal structure with structural parameters of 10.23 angstrom and 9.93 angstrom, respectively. Infrared and Mo center dot ssbauer spectra indicated that part of FeIIILS-CN-CoIIHS were transformed to FeII LS-CN-CoIII LS configuration when preparation temperature rises to 80 degrees C. It indicated that preparation temperature induced charge transfer from CoII to FeIII ions occurred in present sample. Magnetic analysis showed that these cobalt iron cyanides are both ferrimagnetic. The difference of magnetic moments between the two compounds over the entire temperature range is ascribed to the fact that [KCoFe]RT has more paramagnetic central ions than [KCoFe]80 degrees C. The difference between room temperature theoretical and experimental magnetic moments may be attributed to the weak spin-orbit coupling existing for both ions.

Automated summary

The K0.4Co1.3[Fe(CN)6]·nH2O samples prepared by co-precipitation method exhibit different crystal phase structures and magnetic properties at different temperatures. At 80 degrees C, part of FeIIILS-CN-CoIIHS transformed to FeIILS-CN-CoIIILS configuration, and charge transfer occurred from CoII to FeIII ions, resulting in the discrepancy between experimental and theoretical magnetic moments at room temperature.