Anomalous Photomagnetization Behaviors under a Large field in Ternary Metal Prussian Blue Analogues KαMnCo(1–x)[Fe(CN)6]β·nH2O

Cobalt–iron Prussian blue analogues are typical materials with a photomagnetic effect, capable of exhibiting significant magnetic polarization enhancement upon exposure to light. In this work, upon replacing Mn in Co-ion sites, the obtained K_αMn_xCo_(1–x)[Fe(CN)₆]_β·nH₂O Prussian blue analogues displayed an anomalous behavior of photoinduced magnetization changes, which correlates with the content of substituted Mn ions. Especially, for compounds with x ≥ 0.34, the photoexcitation led to the emergence of a novel demagnetization process characterized by a reduction in magnetic moments, which has not previously been reported. This phenomenon can be explained by the mechanism named spin down of Mn ions driven by metal-to-metal charge transfer (MMCT) between Fe and Co, wherein the bond elongation induced by MMCT between Fe and Co compresses the bond of the Mn ion, causing the rearrangement of spin in the Mn ion and eventually resulting in demagnetization.