Magnetically bistable solid solutions of Prussian blue analogues with chemical formulas of KaNi1-xCox[Fe(CN)(6)](beta)center dot nH(2)O (Ni1-xCoxFe) and K alpha Co gamma[Fe(CN)(6)](y)[Cr(CN)(6)](1-y)center dot nH(2)O (CoFeyCr1-y) have been synthesized and studied using mass spectrometry, Mossbauer spectroscopy, X-ray diffraction, temperature-dependent infrared spectroscopy, and dc magnetometry. These compounds provide insight into interfaces between the photomagnetic Co-Fe Prussian blue analogue and the high-T-C Ni-Cr Prussian blue analogue that exist in high-T-C photomagnetic heterostructures. This investigation shows that the bistability of Co-Fe is strongly modified by metal substitution, with Ni1-xCoxFe stabilizing high-spin cobalt-iron pairs and CoFeyCr1-y stabilizing low-spin cobalt iron pairs, while both types of substitution cause a dramatic decrease in the bistability of the material.