Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets

Abstract

We present longitudinal field muon spin relaxation $(\ensuremath{\mu}\mathrm{SR})$ measurements in the unilluminated state of the photosensitive molecular magnetic $\mathrm{Co}\text{\ensuremath{-}}\mathrm{Fe}$ Prussian Blue analogues ${M}_{1\ensuremath{-}2x}{\mathrm{Co}}_{1+x}[\mathrm{Fe}(\mathrm{CN}{)}_{6}]∙z{\mathrm{H}}_{2}\mathrm{O}$, where $M=\mathrm{K}$ and Rb with $x=0.4$ and $\ensuremath{\simeq}0.17$, respectively. These results are compared to those obtained in the $x=0.5$ stoichiometric limit ${\mathrm{Co}}_{1.5}[\mathrm{Fe}(\mathrm{CN}{)}_{6}]∙6{\mathrm{H}}_{2}\mathrm{O}$, which is not photosensitive. We find evidence for correlation between the range of magnetic ordering and the value of $x$ in the unilluminated state, which can be explained using a site percolation model.