Pressure-induced sequential magnetic pole inversion and antiferromagnetic-ferromagnetic crossover in a trimetallic Prussian blue analogue

The flexibility of the structure of Prussian blue analogues and its ability to incorporate a variety of competing magnetic interactions have allowed the design of mixed ferro-ferrimagnets, which span the whole spectrum of magnetic behavior, including the rare phenomenon of magnetization reversal in response to a change in temperature. Hydrostatic pressure is used here to induce multiple reversals of the direction of the spontaneous magnetization in the trimetallic Prussian blue analogue, Rb_0.64Ni_0.31Mn_0.87[Fe(CN)₆]·2.8H₂O. Remarkably, the magnetic response is extremely sensitive to pressure, and the magnetization flips from positive to negative and back to positive in a very narrow pressure range (0 < P < 0.6 kbar). A further increase in pressure to 4.0 kbar induces an internal redox reaction, and the magnetic order switches from ferrimagnetic to bulk ferromagnetism.