Structure characterization and magnetic behavior of NaNi4(PO4)(3) and KMn4(PO4)(3)

New sodium nickel and potassium manganese orthophosphates NaNi4(PO4)(3) (ab breviated as NNP) and KMn4(PO4)(3) (KMP) with tunnel structures have been s ynthesized. They crystallizes in the orthorhombic space group Pnmm with a = 6.148(6) Angstrom, b = 16.210(1) Angstrom, c = 9.479(4) Angstrom for (NNP) , and 6.554(8) Angstrom, b = 16.04(9) Angstrom, c = 9.977(2) Angstrom for ( KMP). The structure is built up from trinuclear groups of edge-sharing MO6 octahedra, giving rise to the [M3O11](infinity) chains running along the [1 00] direction. Both materials show antiferromagnetic interactions and exhib it spontaneous magnetization at low temperatures, which can be explained by a canting of spin arrangement, giving rise to a weak ferromagnetic compone nt. This behavior can be interpreted on the basis of structural features an d the characteristics of single-ion intercalations. (C) 1999 Academic Press .