Magnetism and the magnetic structure of the pillared perovskite, La5Re3MnO16

The new, pillared perovskite material, La5Re3MnO16, has been synthesized by a somewhat modified method than that published previously (J. Solid State Chem. 151 (2000) 31) in sufficient quantities for neutron diffraction experiments. Such experiments were carried out between 10 and 250 K at zero applied field. The crystal structure found at 250 K from refinement of powder neutron diffraction data is in excellent agreement with previous results obtained from a single crystal X-ray experiment. Bulk susceptibility measurements show a sharp spike at 161 K and a broad maximum at ∼100 K. Long range magnetic order was found below the critical temperature of ∼165 K with an ordering wave vector, k=(0012). The magnetic structure found consists of perovskite type layers containing Re5+ and Mn2+ moments coupled ferrimagnetically (Re antiparallel to Mn) within the layers and with antiferromagnetic interlayer coupling. The ordered moments at 10 K are 4.0(1)μB for Mn2+ and 1.0(1)μB for Re5+, not unreasonable values. The Re moments lie nearly along the c-axis while the Mn moments make a angle of ∼18° with respect to c. While most of the magnetic scattering can be accounted for by the above model, two weak reflections are seen which appear at 90 K and below and require k=(121212).