Antiferromagnetic order and consequences on the transport properties of Ba4Ru3O10

Barium ruthenate Ba₄Ru₃O₁₀, in which Ru₃O₁₂ trimers are connected together to form a checkered two-dimensional framework, has been synthesized and its structural, magnetic, and transport properties studied between 300 and 2 K. The paramagnetic to antiferromagnetic transition at T_N ≈ 105 K evidenced on the susceptibility curve coincides with an increase of electron localization in transport measurements. Thermoelectric power and Hall coefficient measurements both exhibit dramatic changes at T_N, characteristic of a reconstruction of the bands structure near the Fermi level. No pronounced structural changes are observed at T_N in this compound. The magnetic scattering signal on the neutron powder diffraction patterns below T_N is weak but can be tentatively modeled with an antiferromagnetic ordering of the spins at both ends of a trimer, the spin of the more symmetric Ru site remaining idle. Crystal field and strong spin-orbit coupling at the Ru⁴⁺ site seem to be the key parameters to understand the magnetic state of Ba₄Ru₃O₁₀.