Neutron diffraction study of the magnetic structure of Na<Subscript>2 </Subscript> <Emphasis Type="Bold">RuO <Subscript>4</Subscript>

Nuclear and magnetic structures of sodium ruthenate (VI) have been studied by neutron powder diffraction in the temperature range 1.5–200 K. Na<Subscript>2</Subscript>RuO<Subscript>4</Subscript> crystallizes in the monoclinic structure, with space group P 2<Subscript>1</Subscript>/c. The structure consists of apical corner sharing RuO<Subscript>5</Subscript> trigonal bipyramids forming infinite chains running along the b axis. These infinite [ RuO<Subscript>3</Subscript>O<Subscript>2/2</Subscript>] chains form a pseudo hexagonal close packing of rods with Ru–Ru distances of 3.51 Å within the chains and 5.30–5.47 Å between the chains. At T<Subscript>N</Subscript>=37.2 K a magnetic transition leads to an antiferromagnetic state. The Ru<Superscript>6+</Superscript> magnetic moments are ordered antiferromagnetically along the chains (b-axis), while the inter-chain interaction is ferromagnetic. A classical infinite chain model was fitted to the magnetic susceptibility data in order to estimate the strength of the nearest-neighbor exchange interactions along and between the chains, resulting in an intrachain coupling parameter of 2J=-86 K, and an interchain parameter J<Subscript>⊥</Subscript> with <InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\vert $</EquationSource> </InlineEquation>2J<Subscript>⊥</Subscript> <InlineEquation ID="Equ2"> <EquationSource Format="TEX">$\vert $</EquationSource> </InlineEquation> = 3 K. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2006