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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
2(1)/c. The structure consists of apical corner sharing RuO5 trigonal
bipyramids forming infinite chains running along the b axis. These
infinite [RuO3O2/2] chains form a pseudo hexagonal close packing of
rods with Ru-Ru distances of 3.51 angstrom within the chains and
5.30-5.47 angstrom 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(perpendicular to) with \2J(perpendicular to)\ = 3 K.
