Synthesis, structures and magnetic properties of the new vanadates AgMnVO4 and RbMnVO4

The new compounds, AgMnVO4 and RbMnVO4 have been synthesized by solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data for RbMnVO4 and powder X-ray diffraction data for AgMnVO4. AgMnVO4 crystallizes with the maricite-type structure in space group Pnma, a=9.5778(6) Å, b=6.8518(4) Å, c=5.3734(3) Å and Z=4. RbMnVO4 crystallizes in space group P63 with a stuffed tridymite-type structure, a=11.2584(3), c=8.9893(13) Å and Z=8. A merohedral twinning was taken into account for its structural refinement. To our knowledge this is the first vanadate showing this structural type. AgMnVO4 and RbMnVO4 were characterized by magnetic susceptibility and specific heat measurements. AgMnVO4 is antiferromagnetic with a Néel temperature of 12.3 K determined by specific heat measurements. RbMnVO4 exhibits canted antiferromagnetism with a Néel temperature of 6.5 K.