X-ray absorption study of structural coupling in photomagnetic prussian blue analogue core@shell particles

X-ray absorption spectroscopy experiments of core@shell, photomagnetic, and Prussian Blue analogue heterostructures obtain the local structure around the magnetic transition-metal ions before and after illumination. Two samples, containing nickel hexacyanochromate (Ni-Cr) and cobalt hexacyanoferrate (Co-Fe) in Ni-Cr@Co-Fe and Co-Fe@Ni-Cr geometries, were studied. Both materials display the well-known photoinduced valence tautomerism for Co-Fe, accompanied by a large change in cobalt to nitrogen distances. Furthermore, these experimental results show a structural coupling of the photoactive Co-Fe layer to the passive Ni-Cr layer. Finally, the strain across the heterostructured interface in Co-Fe and Ni-Cr containing core@shell models is investigated with simulations that use custom potentials derived from density functional theory calculations.