Vacancy-driven magnetocaloric effect in Prussian blue analogues

We experimentally show that the magnetocaloric properties of molecule-based Prussian blue analogues can be adjusted by controlling during the synthesis the amount of intrinsic vacancies. For Cs_xNi^II_4[Cr^III(CN)_6]_(8+x)/3}, we find indeed that the ferromagnetic phase transition induces significantly large magnetic entropy changes, whose maxima shift from 68 K to 95 K by varying the number of [Cr^III(CN)_6]^3- vacancies, offering an unique tunability of the magnetocaloric effect in this complex.