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

Abstract

The K0.4Co1.3[Fe(CN)6]•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℃([KCoFe]80℃), 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 Å and 9.93 Å, respectively. Infrared and Mössbauer spectra indicated that part of FeLSIII–CN-CoHSII were transformed to FeLSII–CN-CoLSIII configuration when preparation temperature rises to 80℃. 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℃. The difference between room temperature theoretical and experimental magnetic moments may be attributed to the weak spin–orbit coupling existing for both ions.