MAGNETIC-PROPERTIES OF THE M(PO3)(3) (M=TI, V) METAPHOSPHATES

Two metaphosphates with the formula M(PO3)(3) (M = Ti and V) have been synthesized and characterized. Their crystal structures consist of is olated MO6 octahedra linked through infinite [PO3](infinity) chains of PO4 tetrahedra. The IR and UV-VIS results for these compounds are con sistent with chain structures in which the Ti-III and V-III cations ex hibit octahedral symmetry. The EPR spectrum of the titanium metaphosph ate at 4.2 K shows a nearly Lorentzian signal centred at g = 1.77, whi ch disappears at 100 K. EPR results obtained for the doped Sc(PO3)(3): 0.1% Ti-III metaphosphate are discussed on the basis of an effective t rigonal symmetry. For the vanadium metaphosphate, the EPR spectrum exh ibits a weak signal attributed to V3+ ions, with a zero-field splittin g parameter D estimated at between 2 and 8 cm(-1). Magnetic measuremen ts show ferromagnetic and antiferromagnetic interactions for the titan ium and vanadium metaphosphates, respectively. A value of J/k = -0.92( 2) K has been obtained by fitting the experimental magnetic curve for V(PO3)(3) to an analytical expression deduced for a three-dimensional Heisenberg model.