Photoinduced Magnetism in Nanoscale Heterostructures of Prussian Blue Analogues*

Nanometer-scale cubic heterostructures of two Prussian blue analogues, ferromagnetic K$_j$Ni$_k$[Cr(CN)$_6$]$_l \cdot$\emph{n}H$_2$O (\textbf{A}) with $T_c\sim70$~K and photo-active ferrimagnetic Rb$_a$Co$_b$[Fe(CN)$_6$]$_c \cdot$\emph{m}H$_2$O (\textbf{B}) with $T_c\sim20$~K, have been studied.\footnote{M. F. Dumont \emph{et al.}, Inorg. Chem., submitted.} These samples exhibit a persistent photoinduced decrease in magnetization at temperatures up to $T_c\sim70$~K of the \textbf{A} constituent, resembling results from analogous \textbf{ABA} heterostructured films.\footnote{D. M. Pajerowski \emph{et al.}, J. Am. Chem. Soc. \textbf{132}, 4058 (2010).} This net decrease suggests that the photoinduced structural transition in the \textbf{B} layer generates a strain-induced decrease in the magnetization of the \textbf{A} layer, similar to a pressure-induced decrease previously observed in the pure \textbf{A} material.\footnote{M. Zentkov\'{a} \emph{et al.}, J. Phys.: Condens. Matter \textbf{19}, 266217 (2007).} Core-shell and core-shell-shell configurations \textbf{AB}, \textbf{BA}, \textbf{ABA}, and \textbf{BAB} have been characterized by TEM, FTIR, XRD, and SQUID magnetometry.\\[4pt]*Supported, in part, by NSF DMR-0701400 (MWM) and DMR-1005581 (DRT), NSERC, CFI, the NHMFL, and the State of Florida.