Magnetism and the magnetic structure of the pillared perovskite, La_5Re_3MnO_(16)

摘要

The new, pillared perovskite material, La_5Re_3MnO_(16), 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 approx 100 K. Long range magnetic order was found below the critical temperature of approx 165 K with an ordering wave vector, k = (0 0 1/2). The magnetic structure found consists of perovskite type layers containing Re~(5+) and Mn~(2+) 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) mu_(B) for Mn~(2+) and 1.0(1) mu_(B) for Re~(5+), not unreasonable values. The Re moments lie nearly along the c-axis while the Mn moments make a angle of approx 18 deg 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 = (1/2 1/2 1/2).