Observation of the interplay between Photoinduced Magnetisation and Pressure Induced Electron Transfer in Cobalt Hexacyanoferrate Prussian Blue Analogue*

The Prussian blue analogue K${}_{i}$Co[Fe(CN)${}_{6}$]${}_{j}$$\cdot$nH${}_{2}$O (CoFe-PBA) has been studied in both its light and dark states as a function of pressure up to 2.23~GPa. The material is known to undergo photoinduced magnetization (PIM) where irradiation leads to an increase in magnetization.\footnote{O. Sato \textit{et al.} Science \textbf{272} (1996) 704.} On the other hand, application of pressure results in a pressure induced electron transfer (PIET) where a decrease in magnetization is observed.\footnote{V. Ksenofontov \textit{et al.} Phys. Rev. B \textbf{68} (2003) 024415.} Both phenomena involve a spin transition between the low spin $(S=0)$ and the high spin $(S=2)$ states, and our work encompasses the application of both light and pressure to study the interplay between these two external stimuli. Our magnetic results indicate the suppression of the PIM at 2.23~GPa, but below this pressure, the coexistence of PIET and PIM is observed. Furthermore, in the high temperature region, we observe a increase in the temperature at which the charge transfer induced spin transition (CTIST) occurs.\footnote{N. Shimamoto \textit{et al.} Chem. Lett. \textbf{31} (2002) 486.}