Photoinduced perturbations of the magnetic superexchange in core@shell Prussian blue analogues

Cubic heterostructured core@shell particles of Prussian blue analogues, composed of a shell (similar to 80 nm thick) of ferromagnetic K0.3Ni[Cr(CN)(6)](0.8)center dot 1.3H(2)O (A), T-c similar to 70 K, surrounding a bulk (similar to 350 nm) core of photoactive ferrimagnetic Rb0.4Co[Fe(CN)(6)](0.8)center dot 1.2H(2)O (B), T-c similar to 20 K, have been studied. Below nominally 70 K, these CoFe@NiCr samples exhibit a persistent photoinduced decrease in low-field magnetization, and these results resemble data from other BA core@shell particles and analogous ABA heterostructured films. This net decrease suggests that the photoinduced lattice expansion in the B layer generates a strain-induced decrease in the magnetization of the NiCr layer, similar to a pressure-induced decrease observed by others in a similar, pure NiCr material and by us in our CoFe@NiCr cubes. Upon further examination, the data also reveal a significant portion of the NiCr shell whose magnetic superexchange, J, is perturbed by the photoinduced strain from the CoFe constituent. (C) 2013 Elsevier Ltd. All rights reserved.