Neutron diffraction study of the magnetic structure of Na₂ RuO ₄

Abstract.

Nuclear and magnetic structures of sodium ruthenate (VI) have been studied by neutron powder diffraction in the temperature range 1.5–200 K. Na₂RuO₄ crystallizes in the monoclinic structure, with space group P 2₁/c. The structure consists of apical corner sharing RuO₅ trigonal bipyramids forming infinite chains running along the b axis. These infinite [ RuO₃O_2/2] 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_N=37.2 K a magnetic transition leads to an antiferromagnetic state. The Ru⁶⁺ 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_⊥ with $\vert$2J_⊥ $\vert$ = 3 K.