Synthesis and characterisation of the quaternary nitride-fluoride Ce2MnN3F(2-delta).

Ce(2)MnN(3)F(2-delta) has been synthesised via low-temperature fluorination of the ternary nitride Ce(2)MnN(3). To the best of our knowledge, Ce(2)MnN(3)F(2-delta) is the first quaternary nitride-fluoride to be reported. The reaction of Ce(2)MnN(3) with 10% F(2)/N(2) at 95-115 degrees C yields the fluorinated phase Ce(2)MnN(3)F(2-delta), with tetragonal symmetry (P4/nmm a = 3.8554(4) A and c = 13.088(4) A based on neutron powder diffraction), accompanied by starting material. Rietveld refinement supports a staged fluorine insertion reaction (into alternate rocksalt layers) to give a product with stoichiometry Ce(2)MnN(3)F(2-delta). A comparison with the formation of Sr(2)TiO(3)F(2) and the isostructural LaSrMnO(4)F indicates that two F(-) anions are inserted but no F(-)/N(3-) substitution takes place. Magnetic susceptibility measurements show a transition from Pauli paramagnetic behaviour, in Ce(2)MnN(3), to paramagnetic behaviour upon fluorination. The effective magnetic moment in Ce(2)MnN(3)F(2-delta), mu(eff) = 5.38 mu(B), is consistent with an intermediate value between that of Mn(3+) (4.9 mu(B)) and Mn(2+) (5.9 mu(B)) supporting the proposed stoichiometry, Ce(2)MnN(3)F(2-delta).