Pressure-induced phase transition in a molecule-based magnet with interpenetrating sublattices

The molecule-based magnet [Ru2(O2CMe)4]3[Cr(CN)6] contains two interpenetrating sublattices with sublattice moments confined to the cubic diagonals. At ambient pressure, a field of about 850 Oe rotates the antiferromagnetically coupled sublattice moments toward the field direction, producing a wasp-waisted magnetization curve. Up to 7 kbar, the sublattice moments increase with pressure due to the enhanced exchange coupling between the Cr(III) and Ru(II/ III)2 spins on each sublattice. Above 7 kbar, the sublattice moment drops by about half and the parallel linear susceptibility of each sublattice rises dramatically. The phase transition at 7 kbar is most likely caused by a high-to-low-spin transition on each Ru2 complex.