Crystal structure and absence of magnetic order in single-crystalline RuO2

RuO2 was considered for a long time to be a paramagnetic metal withan ideal rutile-type structure down to low temperatures, but recent studies onsingle-crystals claimed evidence for antiferromagnetic order and some symmetrybreaking in the crystal structure. We have grown single-crystals of RuO2 byvapor transport using either O2 or TeCl4 as transport medium. These crystalsexhibit metallic behavior following a T2 low-temperature relation and a smallparamagnetic susceptibility that can be attributed to Pauli paramagnetism.Neither the conductance nor the susceptibility measurements yield any evidencefor a magnetic or a structural transition between 300K and ∼4 K. Comprehensivesingle-crystal diffraction studies with neutron and X-ray radiation reveal the rutilestructure to persist until 2K in our crystals, and show nearly perfect stoichiometry.Previous observations of symmetry forbidden reflections can be attributed tomultiple diffraction. Polarized single-crystal neutron diffraction experiments at1.6K exclude the proposed antiferromagnetic structures with ordered momentslarger than 0.01 Bohr magnetons.