Double-layered ruthenate Sr3Ru2O7F2 formed by fluorine insertion into Sr3Ru2O7

A new compound with the composition of Sr3Ru2O7F2 has been obtained by fluo rination of the double layered Ruddlesden-Popper phase, Sr3Ru2O7 Neutron po wder diffraction (NPD) reveals that due to a similar rotation of RuO6 octah edra, the structure of Sr3Ru2O7F2 can be described with the same space grou p Pban as Sr3Ru2O7 but with a large expansion in the c axis and slight cont raction in the ab plane [a=5.4231(4) Angstrom, b=5.4168(4) Angstrom, and c= 24.2505(8) Angstrom, 290 K]. The fluorinated ruthenate retains the layer st ructure: F occupies the interstitial sites in the rock salt layer leaving t he double RuO layer intact. NPD at 2 K shows that Sr3Ru2O7F2 is antiferroma gnetic, with a G-type ordering of the Ru spins and an ordered moment of mu( z) = 1 mu(B)/Ru along the c direction. Magnetization measurements implies a small ferromagnetic moment below 185 K, which is attributed to canting of the Ru spins from the c axis.