Photoinduced effects on the magnetic properties of the (Fe0.2Cr0.8)1.5[Cr(CN)6] Prussian blue analogue

Abstract

One of the most attractive characteristics of some Prussian blue derivatives is the sensitivity of their magnetic properties to the irradiation with light. In this work photoinduced effects in the (Fe_0.2Cr_0.8)_1.5[Cr(CN)₆]·15H₂O PBA have been studied by means of X-ray-based spectroscopies and magnetometry. It is found that the photosensitivity of this compound is mostly centred on the Fe cations: the exposure to green light induces a transfer of electrons from them to the Cr that provokes a reversal of the previously existing linkage isomerization and increases the elastic strain caused by the misfit of the unit cells of the Fe–NC–Cr and Cr–NC–Cr sublattices. The green light also quenches the magnetism of the Fe^II high-spin (HS) ions present in the sample and reduces the magnetic moments of most of the Cr cations except for Cr^II HS. Our study highlights the important role played by the mismatch between the unit cells of the coexisting sub-lattices in ternary Prussian blue analogues.