Photoinduced ferrimagnetic systems in Prussian blue analogues C-x(I)Co-4[Fe(CN)(6)](y) (C-I = alkali cation). 1. Conditions to observe the phenomenon

Photoinduced magnetization has been recently evidenced by Hashimoto et al. in CoFe Prussian blue analogues. We synthesized three compounds with a vari able cobalt environment to point out the conditions required to observe the photoinduced magnetization. Structure and electronic structure of the comp ounds have been investigated combining XANES, infrared spectroscopy, and po wder X-ray diffraction experiments. Magnetization as a function of temperat ure before and after irradiation showed that diamagnetic pairs Co-III-NC-Fe -II are necessary for the existence of the photoinduced magnetization, but their presence is not a sufficient condition. The role of hexacyanoferrate vacancies in the phenomenon is pointed out.