Weak Ferromagnetism and Framework Switching in KMnHP3O10

Polycrystalline KMnHP3O10 has been prepared from solution. It adopts a triclinically distorted variant of the RbMnHP3O10 structure and an approximate structure refinement has been obtained from powder neutron diffraction data (space group P , a= 7.102(2), b=7.234(1), c=9.109(2) ?, =72.176(8), =73.762(9), =70.642(12)° at 2 K). A magnetic ordering transition is observed at 15 K, below which KMnHP3O10 displays weak ferromagnetism with a net moment of ~0.3 B per Mn ion showing that the true structural symmetry may be P1. The magnetic structure has an a×2b×2c supercell and is more complex than that of the Rb and Cs analogues, due to a switching of the Jahn–Teller distortions of the MnO6 octahedra.